Very good concept! Although the Introduction to the mechanics could have been a bit better ^^’ I was struggling at first. The only bug i found so far is that you can scan items multiple times. I think paying/giving out change and better implementation of the receipt are the first steps I would tackle, if I would work on the game. But I think this project could go very far if done right :P
Edit: Found another bug that lets you rip off the receipt without anything on it yet