Am I the only one who hates to see this: 100$ For those who don't realize it, the $ goes before the amount, not after. If you're quoting dollars, put it before. If you're quoting your local currency, put it wherever you want.
Then in German language it could be something like 21 - zwanzig und eins (twenty-one) instead of 21 - ein und zwanzig (one and twenty, which is correct) But still, I think 100$ has more sense, just like this correction in the German language
It's just because people are used to it this way. In most of the other countries the currency sign is put after the amount. It often happens to me to write it the wrong way and then to go back and correct it.