Negotiate, but allow these people to make a living. A dollar here and there means little to us, and much more to them. I like to negotiate hard so I know I'm getting the very best deal, then pay a little extra by choice. I don't mind being generous, but do not like being taken advantage of. I don't give hand outs, but always tip well.
There's a young guy, 16 or 17 and very hard working, who busses tables and helps the waitress at Coco. I always slip him a $5 in case the wait staff aren't as generous with him.