reading aloud - How should numbers be spelled on a receipt?

One of the most confusing things for me is spelling English numerals.

What is grammatical way to spell the following numbers in the context of writing the numeral in a receipt?

$100 — a hundred dollars or one hundred dollars?
$201 — two hundred [and?] one dollar[s?]?
$1500 — fifteen hundred dollars or one thousand five hundred dollars?

$1525 — fifteen twenty-five dollars or [one/a] thousand five hundred twenty-five dollars?

Also, is there any difference between UK and US systems? If so, what are they and what system do I use in a non-English speaking country?

Answer

I'm British, but I can answer for the UK and US:

$100 — a hundred dollars or one hundred dollars?

"A hundred dollars" is how I'd say it in speech. "One hundred dollars" is how I'd write it on a cheque.

$201 — two hundred [and?] one dollar[s?]?

In the UK we'd say "two hundred and one dollars". In the US, they might say "two hundred one dollar[s]".

$1500 — fifteen hundred dollars or one thousand five hundred dollars?

"Fifteen hundred dollars" is how I'd say it in speech. The more "proper" way to say it, and the way I'd write it on a cheque is: "One thousand, five hundred dollars" (never "one thousand and five hundred dollars").

$1525 — fifteen twenty-five dollars or [one/a] thousand five hundred twenty-five dollars?

I'd never say "fifteen twenty-five dollars", I'd either say "Fifteen hundred and twenty five dollars", or "one thousand, five hundred and twenty five dollars". Americans might skip the "and".

For a non-English speaking country, say the number fully using "one", for the sake of clarity. In some countries though (such as the Netherlands and Norway), the use of "fifteen hundred" etc. is the same in that language too.