Every time we fill up our tanks, we wrestle with one of life’s thorniest mysteries: Why do gas prices end in 0.9 cents? Unfortunately, the origins of the increment are murky. Some sources attribute the practice to the 1920s and 1930s, when the gasoline tax was nine-tenths of a cent.
Stations would simply slap the extra 0.9 onto the advertised price of a gallon to give Uncle Sam his cut. Others theorize that slashing 0.1 cent off the price undercut competitors back in the days when gas was just a few cents per gallon.
Although most drivers simply ignore the extra 0.9 cents, oil companies certainly don’t. In 2009, Americans consumed 378 million gallons of gas per day, and that extra 0.9 cents per gallon was collectively worth nearly $3.5 million a day. On the flip side, you could also argue that customers collectively saved around $340,000 per day, thanks to stations’ reluctance to round up to the next penny.