A Good tip estimator is Tip N Split...I know it's easy just to double the tax but this app does more. You can log in how much percent
you want to give for the service you receive. It shows how much the tip is but the little extra this tip estimator has is you can log
in the number of the people at the table and it figures in how much each would pay and it includes the tip. So if everyone orders the same
or a meal about the same it's easy to figure up each owes..Of course it's a free App. for Android and IPhone.....