You know what I hate even more than what you described (I too have never been able to get them to use the 50% instead of the sale), is some of my joann's have older systems and if you don't tell them which item you want the coupon to apply to, it'll just apply to the last thing rung in before the coupon was rung in. So if I have something worth $60 and it's the first thing rung, then i buy a piece of candy for $1 and that's rung next, then they decide that would be a good time to use the coupon, the coupon applies only to the $1 item. Now in my example it's pretty obvious what happened, but if I'm buying like 10 things and they're all similar in price, it becomes not so obvious and extremely annoying that their system can't handle the coupon like every other store in the world and just take the 50% off the most expensive thing ...... okay rant over. :)
Rachel