static void OnDiscountAmountChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            PointOfSale me = sender as PointOfSale;

            if (me != null)
            {
                me.RefreshTotals();
            }
        }
        static void OnSelectedPricingModelChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            PointOfSale me = sender as PointOfSale;

            if (me != null)
            {
                if (me.SelectedPricingModel != null && !string.IsNullOrEmpty(me.SelectedPricingModel.Name))
                {
                    Configuration.Current.CurrentPricingModel = me.SelectedPricingModel.Name;
                }
                else
                {
                    Configuration.Current.CurrentPricingModel = string.Empty;
                }
                Configuration.Current.Save();
                me.RefreshTotals();
            }
        }