[nvader]

If you really want to make a deal out of it, you hand it back to the server and ask them to select 0 for you. Mention that you don't think the service deserves a tip, and that you resent being asked.

If enough of us start doing this, it has a chance of applying some back pressure, although unfortunately that force acts through the poorly-paid checkout operator who doesn't directly have the option to influence decisions.