In CORE, based on the country you choose at signup, your default currency, symbols, etc. are customized accordingly (it is set to United States and USD by default). You can specify the full company address in the Settings > Company screen, which determines the default currency for your CORE company, users and clients. You can set your default home or local currency here so that the correct amount, multiplier and symbols are used at relevant places (say, in Expense Entries). If you change the home currency here, the currency on the reports changes automatically and it allows billing your clients in a different currency. This selection can be overwritten at the employee level.
At the Employees (and Vendors) screen level, you can override the default company currency to your location so that correct values and symbols are used everywhere. This currency setting enables your employees/vendors to log expenses in a foreign currency. For example, if you want your Canadian users to log in and enter expenses in the Canadian Dollar (CAD), you can change their currency to CAD at this level.
The above settings can be overwritten at the project level. In the Projects screen, you can set a different currency under General > Billing Options > Terms & Currency section. However, the change in currency only reflects on the invoices of that project, while as the other screens still show the default home currency set in Settings > Company > Information.
CORE also allows you to log and track expenses in multiple currencies. To enter your expenses in a foreign currency, change the Currency field at the expense level in the Expense Entries > Additional tab and specify a Multiplier (exchange rate) for it. Check CORE Help for details on these fields. The Currency screen (Settings > Billing & Invoices) handles the exchange rates and multipliers involved. Be sure to set the most current rates there for the currencies you use. Check this article for details.
Note: Statements are always generated in the home currency of your CORE company.