One of the only places I get take-out regularly is a vegan place called Cafe Gratitude in L.A. I always get the same thing, it's $9.87. I add $2 to the charge slip, $11.87. I also give $$ to beggars sometimes, if I feel like it.
I might as well be Bill Gates compared to the situation of some of these people. To a 20 y.o. trying to live in L.A. or NY and working in a restaurant, an extra several dollars an hour in tips means the difference between paying rent or not. I like being generous, can't stand cheap people and the $2 or $5 means nothing to me.
I also truly believe that my attitude about money brings a ton of it into my life. To each their own.