Gasoline Prices - 9/10?

Why is it that gasoline prices are always listed with a 9/10 next to the price?

Back when there were far fewer stations than there are now, one enterprising soul used this trick to increase sales : “Look, my gasoline costs 9 9/10 cents per gallon! Compared to 10 cents, that’s practically FREE!” Surprisingly, this worked, and everybody started doing it, and now it’s standard and everyone’s afraid to stop.

Others have asked this question, and I wrote a nice post with links. Try searching for it.

It sounds cheaper.

Buy only one gallon at $1.799, though, and you’re paying the whole $1.80, because they round at the register.

Buy ten gallons at $1.799, and you save a whole penny! (You pay $17.99 instead of $18.00.)

Quite some time ago (I think somewhere near Virginia Beach VA) I ran across a station whose prices occasionally ended in other decimal digits. I asked why, and the owner said it was simply a way to look a bit different.