At our grocery stores the cashiers aren't allowed to refund, which sucks IMHO because of course if you don't find an error in time you have to go to the customer service line.
Sorry, but I would have spoke to management.
It's okay to jump...you have wings!
To move forward...you have to stop looking back.
If I didn't want it I would have waited in the line at the counter and got my money back.