<Window x:Class="WpfApp1.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:local="clr-namespace:WpfApp1"
          mc:Ignorable="d"
          Title="MainWindow" Height="300" Width="600">
     <Grid>

          <ScrollViewer>
               <DataGrid AutoGenerateColumns="False"
                    IsReadOnly="True"
                    ItemsSource="{Binding MyData}"
                    FontSize="20">

                    <DataGrid.Columns>
                         <DataGridTextColumn Header="Customer" Binding="{Binding Customer}" Width="150" />
                         <DataGridTextColumn Header="Item" Binding="{Binding Item}" Width="150"/>
                         <DataGridTextColumn Header="Price" Binding="{Binding Price}" Width="150"/>
                    </DataGrid.Columns>
               </DataGrid>
          </ScrollViewer>
         
     </Grid>
</Window>

using System.Collections.ObjectModel;
using System.Windows;

namespace WpfApp1
{
     public class MyShop
     {
          public string Customer { get; set; }
          public string Item { get; set; }
          public string Price { get; set; }
     }

     public partial class MainWindow : Window
     {
          public ObservableCollection<MyShop> MyData { get; set; }
          public MainWindow()
          {
               InitializeComponent();

               // for binding
               this.DataContext = this;

               // data for grid
               MyData = new ObservableCollection<MyShop>()
               {
                              new MyShop() {Customer="ACME", Item="Widget", Price="100"},
                              new MyShop() {Customer="ACME", Item="Widget", Price="100"},
                              new MyShop() {Customer="ACME", Item="Tyre", Price="200"},
                              new MyShop() {Customer="Amazon", Item="Pen", Price="50"},
                              new MyShop() {Customer="Amazon", Item="Paper", Price="20"},
                              new MyShop() {Customer="Autodesk", Item="CAD", Price="10"},
                              new MyShop() {Customer="Autodesk", Item="File", Price="40"},
                              new MyShop() {Customer="ABC", Item="Flowers", Price="503"},
                              new MyShop() {Customer="ABC", Item="Sand", Price="706"},
                              new MyShop() {Customer="ABC", Item="Sea", Price="160"},
                              new MyShop() {Customer="ABC", Item="Home", Price="50"},
                              new MyShop() {Customer="ABC", Item="Nintendo", Price="15"},
                              new MyShop() {Customer="ABC", Item="Eat", Price="23"},
               };
          }
     }
}

<Window x:Class="WpfApp1.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:local="clr-namespace:WpfApp1"
          mc:Ignorable="d"
          Title="MainWindow" Height="300" Width="600">
     <Grid>

          <ScrollViewer>
               <DataGrid AutoGenerateColumns="False"
                    IsReadOnly="True"
                    ItemsSource="{Binding MyData}"
                    FontSize="20"
                    PreviewMouseWheel="MyPreviewMouseWheel">

                    <DataGrid.Columns>
                         <DataGridTextColumn Header="Customer" Binding="{Binding Customer}" Width="150" />
                         <DataGridTextColumn Header="Item" Binding="{Binding Item}" Width="150"/>
                         <DataGridTextColumn Header="Price" Binding="{Binding Price}" Width="150"/>
                    </DataGrid.Columns>
               </DataGrid>
          </ScrollViewer>
         
     </Grid>
</Window>

using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace WpfApp1
{
     public class MyShop
     {
          public string Customer { get; set; }
          public string Item { get; set; }
          public string Price { get; set; }
     }

     public partial class MainWindow : Window
     {
          public ObservableCollection<MyShop> MyData { get; set; }
          public MainWindow()
          {
               InitializeComponent();

               // for binding
               this.DataContext = this;

               // data for grid
               MyData = new ObservableCollection<MyShop>()
               {
                         new MyShop() {Customer="ACME", Item="Widget", Price="100"},
                         new MyShop() {Customer="ACME", Item="Widget", Price="100"},
                         new MyShop() {Customer="ACME", Item="Tyre", Price="200"},
                         new MyShop() {Customer="Amazon", Item="Pen", Price="50"},
                         new MyShop() {Customer="Amazon", Item="Paper", Price="20"},
                         new MyShop() {Customer="Autodesk", Item="CAD", Price="10"},
                         new MyShop() {Customer="Autodesk", Item="File", Price="40"},
                         new MyShop() {Customer="ABC", Item="Flowers", Price="503"},
                         new MyShop() {Customer="ABC", Item="Sand", Price="706"},
                         new MyShop() {Customer="ABC", Item="Sea", Price="160"},
                         new MyShop() {Customer="ABC", Item="Home", Price="50"},
                         new MyShop() {Customer="ABC", Item="Nintendo", Price="15"},
                         new MyShop() {Customer="ABC", Item="Eat", Price="23"},
               };
          }

          private void MyPreviewMouseWheel(object sender, MouseWheelEventArgs e)
          {
               if (e.Handled)
                    return;

               var dataGrid = sender as DataGrid;
               if (dataGrid == null)
                    return;

               var scrollViewer = dataGrid?.Parent as ScrollViewer;
               if (scrollViewer == null)
                    return;

               scrollViewer?.RaiseEvent(new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta)
               {
                    RoutedEvent = UIElement.MouseWheelEvent,
                    Source = sender
               });

               e.Handled = true;
          }
     }
}