There's a workaround that should do what you need. Be sure you've created the discount you need, then when the customer presents the coupoon go to the Item List, find the discount and add it to the sale. It helps to have all your Discounts named consistently so you can search for them by a keyword. All of ours have "Discount" in the name. An even easier solution is to add the Discount Category to one of your screens so you can just touch it to bring up the whole list. When you do it this way the discount applies to the entire sale not an individual item, but assuming your coupons are for fixed amount (like $5 off) that's OK because $5 off an item or $5 off a sale is still $5 off. You can also apply a variable $ or % discount using either of those methods, but again it applies to the whole sale so be careful of % off if you have items that won't be eligible for the discount.
