Does Nassima support multiple currencies?

Yes. Nassima handles multiple currencies for billing and payments, and it isn't something you switch on in one dedicated place — it works through the places you already invoice a customer or take a payment.

For invoicing, Nassima itself supports a wide range of currencies. Creating and sending an invoice in a specific currency, and the full list of currencies available there, is covered under Multi-currency invoicing.

Actually collecting an online payment in a given currency is a different question, and it comes down to your connected payment gateway and your country rather than anything you configure inside Nassima. Each gateway only processes its own set of currencies, so the currencies your customers can actually pay in follow from the gateway you've connected. Setting your business up to accept payments and connecting a payment gateway is covered under Accept payments from your customers.

So the currency you invoice in and the currency you can get paid in online aren't always the same constraint — invoicing is flexible, getting paid depends on your gateway.