public double Round( 
   double value 
)

class MyPage : System.Web.UI.Page
{
    private Dynamicweb.eCommerce.Products.Product product;

    private void Page_Load(System.Object sender, System.EventArgs e)
    {
        product = (Dynamicweb.eCommerce.Products.Product)Session["Ecom.Backend.Product"];
    }

    public double Total(bool IncludeVAT, Dynamicweb.eCommerce.Discounts.Discount.DiscountCalculationType CalculateAs)
    {
        double discountTotal = 0.0;
        double productPrice = 0.0;

        if (IncludeVAT)
        {
            productPrice = product.Price.PriceWithVAT;
        }
        else
        {
            productPrice = product.Price.PriceWithoutVAT;
        }

        if (productPrice <= 0)
        {
            return 0;
        }

        foreach (Discount d in product.Discounts)
        {
            discountTotal += d.get_Value(IncludeVAT, Discount.DiscountCalculationType.DiscountCalculationAmount, false);
        }

        switch (CalculateAs)
        {
            case Discount.DiscountCalculationType.DiscountCalculationAmount:
                return Dynamicweb.eCommerce.Common.Context.Currency.Round(discountTotal);

            case Discount.DiscountCalculationType.DiscountCalculationPercent:
                string tmp = Dynamicweb.eCommerce.Common.Context.Currency.Format((discountTotal / productPrice) * 100, false);
                double ret = 0;
                double.TryParse(tmp, out ret);
                return ret;

            default:
                return discountTotal/productPrice;
        }
    }
}