This is unrelated and mostly just for me.
You need to add your chosen currency to the list of "Available listing currencies" in this add-on's options and then you can use this currency in listings.
If the currency you've picked doesn't use decimal precision, that'll be reflected. There is currently no way to manually adjust or remove the decimal precision if your currency of choice uses decimals (short of custom development).
Note that
in my message here, I was mistaken and thought this add-on didn't actually use the currency formatting built in to XF and thought I'd need to make that change. In actual fact, no change was made for this and the add-on uses the same currency formatting that XF does.