I work in retail & these cards often present issues - but not all of the time. For example if your card is exactly $59 - the cashier has to type in "$59" and then swipe it - they can't just swipe it or their register thinks the card can pay for the whole amount - it will be denied. If the cashier doesn't understand how to prodess this it can be very frustrating!
Another issue with some types of these cards (not all) is that each time you swipe it a service fee comes off -say 50 cents. If they process it wrong & swipe your $59 card for the whole amount & it's denied, you now only have $58.50 left on the card. But you're unaware, so when they then type in $59 and swipe, it still denies it - AND takes another 50 cent fee off for being swiped. Now you're at $58 & you have no idea. So you call the number on the back to see what's up - guess what - there's a 50 cents fee for that too - so they tell you your balance is $58 - the grocery store swipes it for $58 - but you are at $57.50 because of your balance inquiry. And now you're at $57 because they swiped it again. It is insanely frustrating, and I've had it happen in my store to customers at least a dozen times. I swear its a way for them to make money off of these cards!
Bottom line - be sure your purchase is OVER the full amount of your card, and have them type in the exact amount of the card before they swipe it. If your purchase is smaller (say your grocery bill is only $55 this time) - there is sometimes a fee to carry a partial balance, and monthly fees as well - so it's best just to use the entire thing at one shot.