Then you're only tipping 10%. Math is fantastic, isn't it?
I base my tip percentage on the service I recieve. My base starting point is 20% for tips, and it goes up or down from there based on how the service was. If I'm at a place where the waiter was fantastic, I'll go up to around 25% or so.
I also base my tips on the place I'm eating at and what the bill is. For instance, if I'm at the local Japanese resturant, They usually get like 35% tip from me, if not more. They love us there, and are always giving us really fantastic service and free things.
If I'm eating some place and I end up getting a very small bill, I flesh out the tip so the waitress gets a huge tip amount. For instance, if I eat wings at the bar across the street from my house, my bill ends up being $4-$5. The waitresses end up doing a lot of work coming back and forth filling up drinks and taking the bones away and whatnot, so I don't really think it's fair that they do all that for like $1. What I do in this situation is leave $10, which ends up giving the girl about a 50% tip or so.
I don't feel bad about being generous with my tips, as I know these people work hard at what they do.