I am under the impression that gas prices were/are always something-something .9 due to the fact that gasoline pump hoses cannot actually deliver the last bit of gas that has run through the pump(and consequently the analog/digital apparatus that determines the price) and therefore, since the buyer cannot get that last whisper of fuel, the cost gets backtracked 1/10 of a cent. Has anyone ever heard of something like this, or am I just an old fuel? Nyuk, nyuk, nyuk… 
You and a thousand other people believe its not the case. But human psychology, coupled with “this is the way its always been done” proves it every time. When I was in high school the supermarket I was working at priced bananas at 23 cents. People were livid – what were we trying to pull. The typical price was 19 cents a pound, if we priced at 29 cents, maybe they wouldn’t have bought them at that exorbitant price, but the 23, 25 or 27 cents made people furious.
Anytime you want, you can set up a pair of farm stands and set the prices both ways – ending in 9 and ending in 7, and learn that you’re simply mistaken about human psychology.
Except …
This I can’t reconcile. Maybe restaurants are so upscale, we expect the conspicuous consumption, and we don’t mind? Or we figure in the tip and throw all caution to the wind? I got nuthin’
Back in the 70s/early 80s here in PR we got over the issue with the limits on the mechanical counters in pumps by changing to have gas sold by liters (clever, huh?). Yet even so we still had it retail-priced ending at +9/10 of a cent. In the early 00’s then we had a change in the local taxing base (a “temperature expansion adjustment” IIRC) that made the retail prices at the time go to +7/10 and they have stayed that way since in spite of further price and tax changes. So yes there’s that huge element of marketing inertia, of not being seen as pricing differently from the others in the market.
Because there are not enough digits on the display to end it with 99/100 of a cent. The total retail price difference between 2.499 and 2.4999 (1/100 of a cent, or a dollar in $10,000) adds up to about $15-million dollars at the pump per year. Money lost to the retail gas sellers, just by not having enough nines on the display. Of course, they could get that just by charging 2.50, since that would not deter a single sale.
I hate that. It always looks so precious and pretentious, like “we’re so special here at La Ristorante de Cordon Bleu 16, the dollar sign is vulgar to us”.