I think if a shirt is tucked in... if might be ok???
Still... just not a good look.
I used to ***** at my waitresses all the time for stuff like this.
The worst is when they yank a wad of cash from that nifty little crawl space between their boob and armpit to give you change...
This was at a pool hall, but still. Nothing like damp money to make you say, "......just keep it."