There should never be an option below 15%. Having been out with a cheapskate wealthy brother too many times this app has come in handy helping out fixing a bill at a wonderful establishment for a constant "only tip for the meal not the tax" mentality you sadly find yourself related to. Personally would love options to mark where the app was used last - tide to Yelp or something - so you can, hell compete with patrons on giving better tips. In this day and age making a game of being a decent person seems to be the only way to get people to actually help each other out.
Toten-Maske about iHandy Tip Calculator