You can add Extra fee that will apply to subtotal checkout!
Just navigate to Store tab and tap Taxes
Navigate to Extra fee and tap +Add fee
Information you need to specify
Title - Fee title that will be visible to customer
Type - Fixed amount or Percentage
Amount or Percentage rate
Applies to - Extra fee will be added to fulfillment type (Delivery, Pickup, Dine-in)
You can select each and extra fee will be applied on All fulfillment types