If you tip your concrete guy, auto mechanic, roofer and tax man then go ahead and tip, otherwise no. What I'm saying is, tips are not expected. A set price for agreed upon service. That's how I viewed it when I was doing it professionally. Now if you, the customer, think the time turn around, qualtiy, detail, etc that was given is exceptionally above that which was agreeded upon, I'm sure there aint a taxi out there that would turn down a little monetary thank you.