Hi Alex,
RMS has the following tender types:
tenderOther = 0 tenderCash = 1 tenderCheck = 2 tenderCreditCard = 3 TenderAccount = 4 tenderFoodStamp = 6 tenderECCashCard = 7 tenderVoucher = 8 tenderDebitCard = 9
Handling a coupon as cash payment is most definitely incorrect.
Coupon is a form of promotional offer and entitles the bearer a discount on purchase (discount coupon usually w/ no serial number). It is a sales expense on the balance sheet. Because there no "Coupon" tender type in RMS, "Other" is the closest you can get.
Gift Card (or Gift Voucher) on the other hand is different, which is a pre-payment; a liability on the balance sheet waiting to be redeemed. It usually has a serial number or reference number on it for tracking purposes because companies need to know how much liability or worth of the gift cards they need to honor. It is only when the gift card is redeemed is a sale realized or when it expires.
Accounting principles should always be your guidance when selecting the correct tender type.