I stopped trusting my phone's tip split after a server in Denver showed me the math
I used to just hit the 20% button and round up, no thinking. Then a server at a diner off Colfax pointed out the app was taking 20% of the tax too, which came out to about $1.40 extra on a $62 bill. She said people fight her over tips all night and half of it comes from bad phone math. Now I do the 10% in my head, double it, and skip the app. Does the tip button on your phone do this too or is it just the one I use?