There's a little Mex restaurant near where I'm currently camping. Maybe 5 tables, order at the counter... IE most peeps get their food to go. So they've got the CCard swiper at the counter as a payment option, if not cash. There's an LCD touch screen pointed at the customer to complete the details, and even to "sign" at the end.
After okaying the amount + tax, it takes you through the "add tip?" screen. Rather than providing a number pad to key in your desired tip, the options are
conveniently pre-selected for you...
There's a "No tip" button, and the remaining 4 buttons
begin with 15%, then I think 18, 20, & 25%.
Mind you, this is a pick your grub from the big wall mounted menu, order/pay at the counter then stand & wait ~5 mins place; not a sit down & be "waited on" through the duration of your meal restaurant. Those who eat there too, still order at the counter... and
'ideally' they gather up their paper/plastic/tin foil garbage at the end & drop in the trash can by the door.
Also mind you, you select your tip % amount at the
beginning, step #1 of the whole transaction, when you haven't received any "service" or even food, to assess how generously you might tip. So if you've already tipped 15-25%, then you stand waiting 10-15m, and/or they F up your order somehow
(like 'forgetting' the guac as they did my order yesterday!? )... you're SOL.
Naturally there's also the cash tip jar at the counter!