Displayed prices should be the price you have to pay - full stop. No math required or knowledge of local municipal/state/federal tax structures, no required knowledge of local cultural expectations around tipping. Just pay the price. Just because you're accustomed to tax/tip additions doesn't mean they are in any way a good thing that should be preserved.
Because we get that now on most (if not all) grocery stores and retailers. I can see what items in my grocery receipt were charged which of the various local taxes and can dispute them. I've had groceries miss-categorized and considered prepared food which carries a local tax in my area, but they were not prepared foods and should not have been taxed.
Having a full price up front isn't the magical cure a lot of people paint it as.