The best way to end tipping culture is to unionise hospitality workers. As customers, what we need to do is encourage and support working class solidarity, talk loudly about our support for unions, encourage employees to organise, all that kind of stuff.
Mugging is a crime involving an attack on an individual in a public place with the intent to rob them. It typically involves physical assault or the threat of violence to coerce the victim into surrendering their possessions.
Personally I tend to find guns pretty threatening.
The Thieves Guild punchcard: Get 12 muggings and the 13th converts your mugging to a light burgling at the address of your choice! [*]
[*] You must present your punchcard before physical violence begins. If the address to be burgled is a police station, the next mugging will be upgraded to murder. Management takes 75% of all tips. Do not make Management sad. You wouldn't like Management when it is sad.
Interface designers make mistakes, but I don't think they'd make the mistake of allowing a negative sign anywhere on it. You could try for integer overflow, but that's gonna be really bad if you guess wrong.
One time I did come across one of these that popped the whole iPad keyboard up, I tried to enter a negative number and clearly the programers were extra dumb because it managed to crash the whole POS and force a reboot
ETA: cashier thought it was hilarious, store owner got so mad he banned me from the store "for life"