The Weird Penny Hack Behind Every Gas Price Sign — It’s Almost A Cent, Not Quite

Where the 9/10 came from

Back in the early 20th century, gasoline taxes and accounting quirks made it useful to price down to tenths of a cent. When a tax of a penny per gallon mattered a lot (because gas cost pennies), stations learned to advertise prices like 15.9¢ instead of 16¢. That fractional-cent line stuck as signs, systems, and habit.

Why it’s really still there: retail psychology

Humans read prices left-to-right. $3.49 looks a lot nicer than $3.50, even though the real difference is microscopic. That “just-under” effect — the same reason shirts cost $19.99 — nudges drivers toward the pump that looks cheaper.

Competition and thin margins keep it alive

Gas stations make tiny profits on the fuel itself and big money inside the store. In a hyper-competitive market, being perceived as even a hair cheaper can pull business away. No one wants to be the first to round up and look pricier on the corner.

Signage and tech inertia

Pump displays, pricing boards, and point-of-sale systems were built around tenths of a cent. Changing that would be expensive and risk confusing customers trained for decades to expect that weird fraction. So nobody bothers to fix something that “works.”

Does it actually save you anything?

Nope — at that scale the 9/10 is meaningless per gallon unless you’re buying multiple tanks every week. It’s not a real discount; it’s a perception trick. The only people who win are marketers and the guy who picked the font for the roadside sign.