It seems the situation has changed since @Josh Curren posted his A. The same link now shows:

Reporting currencies
Change the currency in my performance reports
You can view your performance reports in a different currency to your
payment currency.
To change your reporting currency:
- In the left navigation, click Performance reports.
- Click the currency drop-down USD ▼ and select a new currency from the list.
Note that when viewing performance reports in a different currency to your payment currency,
monetary values might not be completely accurate due to currency fluctuations.