Create a Pricelist for each currency in Sales -> Products -> Pricelist and set the Country Group and Website (and Currency) accordingly:

For testing purpose you may set Selectable to true as well, so you can switch the Pricelist directly from within the shop.
Note, for this to work, Odoo needs to know where a customer is coming from. This is either based on the customers address - i.e. it must be a logged in customer with an address - or the IP address (might not be accurate).
See also: https://www.odoo.com/documentation/18.0/applications/websites/ecommerce/products/price_management.html#pricelists
Alternatively you could create a second website with a dedicated Pricelist (and therefore Currency) for each website.