At the Sbarro restaurant I work a 'tip' line is printed right on the credit card receipt and a lot of people will write in an amount but we never see any of it. When I first started working there I asked why and was told there was a no tipping policy so I've since advised people that the employees don't receive the tips they are writing in and encourage them not to do so. Why should some fat cat owner of the place get money I deserved for prompt, courteous service?
People that pay in cash will often leave the change from their order with the cashier and it used to be put in a cup and split at the end of the shift. Management put a stop to that too and demanded the change be put in the cash register. Not that I need what amounts to a few bucks at the end of a shift but what the hell, I'm not going to let that fat cat owner get it either, I always give the people their change back.