If communities would like to only allow their country's currency used when suppliers register, Community Administrators and Community Supplier Administrator can disable this settings.
By implementing this change, suppliers can only use your community's country currency during registration and will ensure compliance.
If disabled, any new supplier registrations that go out will not allow suppliers to select any other than your countries currency.
Disable Allow Foreign Currencies
To disable allow foreign currency, go to Administration module > select Suppliers > click Registration tab > under the Default Supplier Setting header, uncheck the Allow Foreign Currencies box.