Your POS will need two keys: a tender or payment key and, if you are selling gift cards, an item or SKU key. The tender key will be just like your cash or credit card tender keys. They will allow you to apply a GiftRocker certificate to a bill.
If you will be issuing Be Our Guest certificates or any other promotional certificate, you may also want to add these as payment keys. This will allow you to track give-a-ways separate from sold certificates.
The the SKU key (Stock Keeping Unit) will allow you account for any cash GiftRocker gift card sales. Selling of gift certificates online or selling where the credit card is charged via your iPhone do not need to be recorded on your POS. Your accountant should capture these transactions directly as proceeds are deposited into your account.