gistfile1.cs

foreach (LineItem item in items)
{
    OrderAddress address = GetAddressByName(form, shipment.ShippingAddressId);
    if (address != null) // no taxes if there is no address
    {
        CatalogEntryDto entryDto = CatalogContext.Current.GetCatalogEntryDto(item.CatalogEntryId, new CatalogEntryResponseGroup(CatalogEntryResponseGroup.ResponseGroup.CatalogEntryFull));
        if (entryDto.CatalogEntry.Count > 0) // no entry, no tax category, no tax
        {
            CatalogEntryDto.VariationRow[] variationRows = entryDto.CatalogEntry[0].GetVariationRows();
            if (variationRows.Length > 0)
            {
                string taxCategory = CatalogTaxManager.GetTaxCategoryNameById(variationRows[0].TaxCategoryId);
                IMarket market = ServiceLocator.Current.GetInstance<IMarketService>().GetMarket(order.MarketId);

                TaxValue[] taxes = OrderContext.Current.GetTaxes(myAppGuid, taxCategory, market.DefaultLanguage.Name, address.CountryCode, address.State, address.PostalCode, address.RegionCode, String.Empty, address.City);
                
                if (taxes.Length > 0)
                {
                    int  itemTax = 0;
                    foreach (TaxValue tax in taxes)
                    {
                        if (tax.TaxType == TaxType.SalesTax) {
                            itemTax = (int)((double)item.ExtendedPrice * (tax.Percentage / 100));
                            totalTaxes += itemTax;
                        }
                    }
                    item[Constants.Metadata.LineItem.VatAmount] = itemTax;
                }
            }
        }
    }
}