OP. You should hear yourself speak.
You said: "For a while you smile through gritted teeth"
But then, today you claim you didn't grin, but had a gritted-teeth business-like expression.
Ao which is it, a smile or a solemn face?
You also repeatedly told us all:
Just thought l'd give him a second chance l suppose
You should also stop using your daughter a a social experiment. Don't keep giving someone a "second chance" out of the supposed kindness of your heart. Who ARE you trying to kid? That's as stupid as allowing a child to play with a dog that has already bitten. You just don't. You choose to protect them from upset instead.
This guy has previously taken her sweets and done the same silly routine.
Just bewilderment that his stage show had moved on a notch!
You say that the cashier has done exactly the same thing before, and then you say that he's moved it up a notch. Well make your mind up, was it the same or was it not?
You then say that This was a while back, she wasn't particularly upset then (if at all) she was much younger /not so aware.
So OP, you need to decide what your story is.
Either he did it before and you gritted your teeth at him but decided to give him a second chance, or he has never done this before because last time you smiled at him and she was totally cool with it but since then he's moved it up a notch.
Either way, its the parent that's the problem here, not the cashier.