When you eat out at a sit-in-non-fast-food-restaurant, what do you usually give for a tip for good service?

I usually drop about $5. I don't believe in 15% gratuity, that's simply too much...damn French. I ate at Genghis Khan restaurant in Crown Casino in Melbourne last year and the bill was a whopping $2500 AU(at the time, about $1300 US). Imagine paying a 15% gratuity for that.