Round totals for currencies

4 min

Rounding is complex because different currencies use different numbers of decimal places.

The following methods return a value with the correct number of decimals, which is determined by the input currency.

Currency.Round()

Currency.Percentage()

Money.Round()

Do not use Math.Round() for rounding. For example, do not use the following code.

var currentCurrency = “JPY” 
    Money itemPrice = new Money(Math.Round(lineItem.ListPrice, 2), currentCurrency);

If you currently use Math.Round, replace it like this.

var currentCurrency = “JPY”
    Money itemPrice = new Money(lineItem.ListPrice, currentCurrency).Round();

Calculate and round an order total

After rounding, use the rounded value for all further totals. For example, here is the correct way to add a number.

var billingCurrency = order.Currency;
    foreach (var item in order.GetAllLineItems())
      {
        var costWithoutDiscount = billingCurrency.Round(item.PlacedPrice * item.Quantity);
        item.Properties["costWithoutDiscount"] = costWithoutDiscount;
      }

Calculate taxes

To get an order‘s correctly-rounded tax amount, do not use the tax amount of individual items. Instead, follow this example.

var billingCurrency = order.Currency;
    var saleTaxesAmount = taxes
      .Where(x => x.TaxType == TaxType.SalesTax)
      .Sum(x => billingCurrency.Percentage(itemPriceWithoutTax, x.Percentage));

In the above code, saleTaxesAmount is returned with a rounded value.

Note Do not use billingCurrency.Percentage(itemPriceWithoutTax, x.Percentage) in other situations