public void getTotal()
{
double discount = Convert.ToDouble(txtdiscount.Text);
double sales = Convert.ToDouble(total_sales.Text);
double vat = sales * pos.vatable();
double vatable = sales - vat;
vatlbl.Text = vat.ToString("#,##0.00");
lblvatable.Text = vatable.ToString("#,##0.00");
lblDisplayTotal.Text = sales.ToString("#,##0.00");
}