Having worked behind a register for many years, I can tell you that paying $6.50 in quarters wouldn't even come close to registering as an unusual purchase. Old ladies cleaning out their purses and paying $12.00 in small change, no quarters - THAT's always annoying and happens far more often than you would believe. They also make the comment, "I know it helps you guys when people pay with change." "Well, actually, we keep about $500 in change in the safe so we don't run out."
For what it's worth, I've paid for $3.xx in gas with loose change, mostly pennies and nickels. It was better than running out of gas (didn't have my debit card with me.)