How can I implement a multicurrency shop? I red some topics in this forum about this feature implementation but I'm not able to implement it.

I can set the desired culture when I add a product to the cart in this way:

ExtendedDataCollection extendedData = new ExtendedDataCollection();
extendedData.AddProductVariantValues(productVariant);
var customerContext = new CustomerContext(UmbracoContext.Current);
var currentCustomer = customerContext.CurrentCustomer;
var basket = currentCustomer.Basket();
basket.AddItem(productVariant.Name, productVariant.Sku, newQuantity, productPrice, extendedData);
basket.Save();

However, I'm not able to set the culture when I add taxes, new shipping and payment methods. In this way code throws an exception: "Invoice is being created with line items costed in different currencies."

My "set payment" code is:

IPaymentMethod paymentMethod = payment.GetPaymentGatewayMethodByKey(payMethodKey).PaymentMethod;
basket.SalePreparation().SavePaymentMethod(paymentMethod);

My "set shipment" code is:

var shippingAddress = basket.SalePreparation().GetShipToAddress();
if (shippingAddress != null)
{
    IShipment shipment = basket.PackageBasket(shippingAddress).FirstOrDefault();
    shipment.VersionKey = Guid.NewGuid();
    basket.SalePreparation().ClearShipmentRateQuotes();
    IShipmentRateQuote quote = shipment.ShipmentRateQuoteByShipMethod(shipMethodKey);
    if (quote != null)
    {
        basket.SalePreparation().SaveShipmentRateQuote(quote);
    }
 }

Is there a way to force to insert a custom price and custom currency (for taxes, shipment and payment)?

Otherwise, is there another way to manage the multicurrency in merchello?