I can Totally sympathize with you. After many wrong amounts being charged to me at JoAnn's I finally learned how to do it.
One thing is that I was told by a sales clerk is that is an item ends in .97 they think it is a sale and don't consider it for the coupon.
The way they do fabric is horrible - the receipt is so confusing that you have no idea of what you are spending. So I keep a small notepad in my purse and as I pick up fabric and I write down the price it should be (the last 3 times I went they tried to charge me as much as 3 times the price and on oters incorrect yardage - bought 1/2yd charged for 1 yd). The one time it amounted to a $10 difference.
Ihave also leaned to just put my coupon off items up front and have her/him ring them up alone and I pay for them. Then I give them everythng else for a 2nd receipt.
I also make especially sure that I write down any super sale price as on my last visit 3 of my items were still in the computer at the much higher price.
I absolutely cringe when I go to the register, but these are things do want, and at the price listed on the shelf, not in their computer. I still like the store, just have to write down the price of everything I put into my cart and watch the register as it rings it up. I want the $$ in my pocket not JoAnn's (besides they evenually get it back on the ext trip any way - hee hee).
Can't honestly remember the last time I went thru the register without having to have them correct a price. But I am still a customer - just Much More Careful / Observant.
Karen