What is with the $100.00 limit at the fuel pumps?

RoyF wrote:
With a 98-gallon aux. tank, I sometimes take more than 100 gallons. I go inside, tell the desk that I want $xxx amount at pump so and so. They swipe the card or I give them case. When I am done, I go back inside and they put the change amount back on the card or give me the change.