The currency shouldn’t be tied to the locale setting.
Here in Europe, some countries have not yet adhered to EUR but use the currency for offers. Invoicing is done in the local currency, but with parity fluctuations it’s better to have EUR as main and until a feature like different invoicing currencies is available, manual invoicing can be used.
We are based in Romania so we set locale to Romania. The currency changed to RON. Because we need EUR we had to change locale to Ireland so that we can retain English language for the GUI and have EUR as currency. Invoicing is done through another app but we use Syncro Invoicing to the convert.