I also try to go with 15% tip as my standard, 18-20% for exceptional service. But I have noticed that receipts and other tip suggestions are starting to pretend

I also try to go with 15% tip as my standard, 18-20% for exceptional service. But I have noticed that receipts and other tip suggestions are starting to pretend that 18% is a bare minimum tip. The tip suggestions on a recent restaurant receipt had calculations for 18, 20, and 25%. It is getting out of hand.