I was at a Denny's off I-25 last Tuesday and ordered two decafs and a regular. The waitress said 'that's cheaper if you get the bottomless mug deal.' I did the math in my head and told her she was off by 47 cents. She pulled out her phone, showed me the app price, and the app price was lower. I sat there doing numbers for 5 minutes before I realized I'd been adding tax twice. How many of you still hand-calculate menu math instead of just using the app?