I've heard Americans say that you need pennies for various reasons, in Australia we don't have pennies, and th?

and the monetary system still works the same without them, when you pay cash, everything is rounded to the nearest 5 cents, and if you pay electronically with a card you pay the exact amount, about the only thing that changed is that my dad started putting exactly $20.02c worth of fuel in the car at the gas station to try and get 2cents worth of free fuel, other than that nothing changed, so seriously, why have pennies when they cost twice as much to make as what the face value is?