Using Toast you may want to setup a minimum order amount before prompting the customer to sign when digital digital receipts. This is a simple process in the Toast Dashboard.
This is most common for counter service restaurants with generally small check amounts (i.e. coffee shops)
Under the Payments section in Toast's back-end, select Payment Options.
Scroll to the Credit section to enter the minimum amount:
Transactions under the amount you designate will not be prompted for a signature when Digital Receipts are turned ON.