Is this system multicurrency?
It will use the currency of your business for purchases, as you don't want to have multiple valuations in the same account.
That said, DL used to have a currency conversion system for purchase orders: a PO would be created in your own currency (so your books are accurate) but you could also show another currency on the PO, the value of which was based on the date's conversion rate. That enabled sending the PO to a vendor in another country, with their own currency value for the item while still keeping your account's books straight.
We've been looking at adding this feature back in for our international uses and if we get enough interest we probably will do so.
It uses the currency of your country when you sign up. I.E. dollars for the USA, Canada, Australia. English Pound for the UK, Euro for countries in the Eurozone, etc.