private void buttonMuffin_Click(object sender, RoutedEventArgs e)
 {
     StoreMenuItem newMuffin = new StoreMenuItem
     {
         ItemName = "Muffin",
         ItemCost = 4.99M
     };
     checkoutList.Add(newMuffin);
     getTotal();
 }
 private void buttonCroissant_Click(object sender, RoutedEventArgs e)
 {
     StoreMenuItem newCroissant = new StoreMenuItem
     {
         ItemName = "Croissant",
         ItemCost = 3.99M
     };
     checkoutList.Add(newCroissant);
     getTotal();
 }
 private void buttonCoffee_Click(object sender, RoutedEventArgs e)
 {
     StoreMenuItem newCoffee = new StoreMenuItem
     {
         ItemName = "Coffee",
         ItemCost = 2.99M
     };
     checkoutList.Add(newCoffee);
     getTotal();
 }
 private void dataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     currentlySelectedItem = (StoreMenuItem)dataGrid.SelectedItem;
 }