As an Australian consumer I'm used to paying in USD and simply seeing a slightly different amount show up on my transaction history (AUD being generally at parity with USD)

Is having multi-currency support important? Does it impact sales? Is using something like money.js to give a close estimate of actual cost good enough?

Whereas the ROTW is pretty much accustomed to being billed in USD online and the impact is far lower.

For me, for my market, AUD+USD are mandatory and optionally GBP/EUR are a strong plus.

I think it helps with localised branding. Sure we are really just one website, with one shipping location (and we aren't hiding this fact). But displaying GBP prices and charging people exactly that price, in the currency they are used to, without any international transaction fee popping up makes a difference.

This, along with creating a local phone number and physical address, gives the customers a better feeling that you are localised to their country.

Of course we haven't actually tested this both ways to see what the difference would be.