Someone

            Dim extPrice As Decimal = 0
            Dim subTotal As Decimal = 0
            Dim totalGst As Decimal = 0
            Dim gstRate As Decimal = 0.05

            For Each aRow As DataRow In Cart.Tables(0).Rows
                extPrice = aRow("Qty") * aRow("Price")
                subTotal += extPrice
            Next

            totalGst = FormatNumber((subTotal * gstRate), 2)