Using multiple Chevron gift cards during a single fill up?

A really random question... I'm looking to save money on gas and have an opportunity to buy multiple Chevron eGift cards, but I must buy $5 at a time to get them at around 15% off.

Does anyone have any experience using multiple gift cards at Chevron (paying either in person or via the app) during a single fill up? As far as I know, I cannot merge these gift cards together. Thanks in advance.