(NEXSTAR) – In case gas prices weren't high enough already, there's always that pesky fraction added onto the end: nine-tenths of a cent tacked on to every gallon.

You'll usually see this odd pricing posted at the gas station (and pretty much nowhere else). After all, it's not like we can pay in fractions of a cent – so why don't gas station just round up? Where does that 9/10 come from anyways?