When trying to fully redeem a $25 VISA gift card from Marriott this afternoon I had problems.
When the restaurant tried to use the card, they put in $25 and it was denied. This was because their machine automatically adds 16% to the amount for an anticipated tip.
To "use up" the card, use at a store or place that tips wouldn't apply. First, pay of the amount due less $25 with cash or another card. That leaves a $25 balance due.
Hand over the gift card and it will empty the card and pay off the balance.
Hope this saves you a hassle.