I think this is most likely up to the store personnel where you purchase. I do recall my coupon had something in the fine print saying it could not be used with any other special offer, and I worried that meant they would not apply it on top of the sale price (the gh was on sale.) But they did, no questions.

I'd be a little surprised if they let you apply two %off coupons to the same item, but you could call them to ask before you buy the coupons.