The policy is 1 coupon per transaction. I don't know if it's programmed into the computer to only accept one at a time, but in the last thread that mentioned the $3 ink coupons there were a couple replies that said they were able to use multiple coupons. So you may be able to con a new cashier into accepting multiple coupons
Otherwise, it's only 1 coupon per transaction.
Edit:
You can bring in 10 at once if you like, you just can't use them all on one purchase. Also, you don't have to give it to the cashier at the time you are purchasing items. If you want you can get your coupon(s) then do your shopping.