People are weird about gasoline. They’ll drive around looking for the cheapest option, to save 2 cents/gallon. Even with a huge tank, that’s less than 50 cents of total savings.
Bless 'em for keeping the price pressure on, but this is so very true. Once I ran a couple of mental hypotheticals, I stopped giving a shit, beyond avoiding places right by airports that jack it up a dollar or more (Las Vegas and especially Orlando, with lots of tourists in rentals, are the worst offenders I've seen).
For a pretty extreme example consider, as you say, a large 25-gal tank, and filling up from dry twice a week, at an average of $0.10/gal non-optimal price: you pay an annual premium of $260 bucks not to drive yourself batty hunting for pennies, and burning at least a tiny bit more fuel to do it. Most people will pay far less. It's just this weird thing that stuck in people's brains long past the point where a cent increase was any significant percentage of the fuel purchase.