US Currency amounts can be formatted, and even calculated, using the $US command, which is triggered by ⌥⇧4 (option-$). The command works backwards from the cursor, looking for the first digit or set of digits that look like they are, or should be, currency. It’s best to run the command soon after you type a currency amount. It will prefix a dollar sign and add a “US” suffix, turning “4” into “$4US.” Pressing the key-combination again will continue to look backwards from the last change. You can move back through the entire current paragraph, but be wary of turning non-currency numbers into currency-formatted strings accidentally.
To highlight the capabilities of this otherwise innocuous command, here’s a movie:
The command will add commas to larger numbers, pad decimals (3.5 becomes $3.50US, 0.5 becomes $0.50US), and round off long fractions. It also executes basic calculations; highlight a calculation and run the command, it will handle most arithmetic and percentage calculations with ease. If you’ve got a product that’s $29 and you want to know what the price would be after a 20%-off coupon, just type “29-20%”, highlight it, and run the command. You’ll get the final total ($23.20US) formatted and ready to go. Don’t try to feed it multi-step calculations, or anything parenthetical, it’s not that smart, yet.
If the selected number contains a Euro symbol at the end (€) or is followed by the word Euro or Euros (case insensitive), a conversion to USD will take place before formatting, using the Italian Bank’s record of the exchange rate as of the day before. This part of the command requires the text to convert to be selected, and does not work backwards through the current line like the other parts of the command. Requires an internet connection.