You can change the invoice currency without having to go into an individual record to update the financial details.
Edit your invoice
Go to Accounts > Invoices > click the 'pencil' to edit your invoice
In the settings panel of your invoice, you have the option of changing the invoice currency. In doing so, it will ask you what the current exchange rate is and provide a link to check the current exchange rates.
Once this information has been added, either in the settings panel or in the artwork details to the left of the settings, it will then let you know what the new price will be. If everything looks correct, simply click 'Done' and the financial details will update automatically.
After you generate the invoice this information will also automatically transfer to the financial details of the artwork record as well.