Tips are added to catering orders through the POS.
If payment is collected at the time of order, a tip selection page should appear after selecting the "Credit/Debit Card" option.
If a tip is not added at that time, you still have the ability to adjust the tip
after-the-fact.
This is done by accessing the ticket through the Ticket History. After accessing the ticket there, there is a button that says "Adjust Tip". You can tap this button to then add a tip to the ticket.