I believe this varies a little state-to-state and even in those (which I think is most?) where it's true they can usually still legally detain you if the have r

I believe this varies a little state-to-state and even in those (which I think is most?) where it's true they can usually still legally detain you if the have reason to believe you're trying to shoplift, though refusal to show a receipt on its own is, obviously, not enough to pass that test. Also workers are unevenly educated on the topic so may try to get in your way or otherwise escalate things if you do this, so take care and stay cool.