I am old enough that when I was a kid in the UK there was still such a thing as a halfpenny (pronounced: ha'penny). Although please note: I am not that old; this was ½p - half a 'new penny', i.e. 1/200 of a pound sterling, and not to be confused with the old ½d, half of an old penny, which was 1/480 of a pound (or two farthings). Predecimal currency was well before my time. By over half a decade, in fact. But anyway, point is: of course this meant that some things were priced to end with £0.99½p. The rules are universal.

Just to add a data point about the pronunciation; the way you've written it leads me to read it as "har-penny", which I imagine is valid, however we pronounced it in my family as "hay-penny".

Sorry, that is indeed the intended pronunciation. In fact even briefer than that: more hayp’ny.

Just wanted to really get across that most importantly, the l and f are definitely both silent.

It's been so long I had completely forgotten about that extra contraction.

Reminds me of one of my favourite coins I had in my possession as a child, a "thrup'ny bit"!

For the uninitiated this was a pre-decimalisation three pence coin.

Only American gas stations. They go so far as to have the 9/10 of a cent fraction as a permanent part of the sign.

French stations too, they’ve introduced the 1.779€ a liter pricing a dozen years ago, so, 4 significant numbers. On a 100€ refill, it’s 10 cents, ie a drop.

Is it always 9/10 of a cent though, or does it vary?

The majority of New Zealand petrol stations display the fractional cent too. Same in Australia from memory.

Oh I didn't know that. They don't do this is Canada. Fuel here is priced to the tenth of a cent (192.5 cents per litre), but it's not fixed to 9/10.

Oh - I misread the comment. It's not fixed - they're all digital.

Apologies.