With the Multi-Currency you can:

Set up separate purchasing/selling currencies: Enterprise users can select the currencies they use for purchasing and selling products on a per-office basis.

Set each project to an individual selling currency: When creating a project, Enterprise users can select the currency that the project is to be sold in. 

Set a default currency per client: Enterprise users can also select a default currency per Client that will populate when creating a new project for that client.

Edit the exchange rate(s) within the project to keep them up-to-date, or to cushion them against volatile market rates over time.