We'd always go out for $3 beers on Thursday (payday) after the shop closed and run a group tab. Our co-worker Matt would leave exactly $3 for each beer, never leaving a tip or accounting for tax. He claimed that people always overpaid in groups, so it'd come out fine for our server. For the most part he was correct, and instead of being a generous tipping group we were a normal tipping group. We went so often over the years that I suspect Matt ended up saving several hundred dollars, but it came at the cost of near constant ridicule from our group. He paid for those $3 beers, and he paid dearly.