diff --git a/addons/account_discount/models/account_invoice.py b/addons/account_discount/models/account_invoice.py
index 16ad498b..f62da34e 100644
--- a/addons/account_discount/models/account_invoice.py
+++ b/addons/account_discount/models/account_invoice.py
@@ -26,7 +26,7 @@ class AccountInvoice(models.Model):
     def _get_total_amount(self):
         for invoice_id in self:
             invoice_id.gross_amount = sum(
-                [line_id.quantity * line_id.price_unit
+                [invoice_id.currency_id.round(line_id.quantity * line_id.price_unit)
                  for line_id in invoice_id.invoice_line_ids])
 
     discount_method = fields.Selection(
diff --git a/addons/purchase/models/account_invoice.py b/addons/purchase/models/account_invoice.py
index 93865444..350cdac7 100644
--- a/addons/purchase/models/account_invoice.py
+++ b/addons/purchase/models/account_invoice.py
@@ -81,9 +81,10 @@ class AccountInvoice(models.Model):
         new_lines = self.env['account.invoice.line']
         for line in self.purchase_id.order_line - self.invoice_line_ids.mapped('purchase_line_id'):
             data = self._prepare_invoice_line_from_po_line(line)
-            new_line = new_lines.new(data)
-            new_line._set_additional_fields(self)
-            new_lines += new_line
+            if data.get('quantity', False) > 0:
+                new_line = new_lines.new(data)
+                new_line._set_additional_fields(self)
+                new_lines += new_line
 
         self.invoice_line_ids += new_lines
         self.payment_term_id = self.purchase_id.payment_term_id
diff --git a/addons/sales_discount/models/sale.py b/addons/sales_discount/models/sale.py
index d42e6504..a7c844c5 100644
--- a/addons/sales_discount/models/sale.py
+++ b/addons/sales_discount/models/sale.py
@@ -26,8 +26,8 @@ class SaleOrder(models.Model):
     def _get_total_amount(self):
         for order_id in self:
             order_id.gross_amount = sum(
-                [line_id.product_uom_qty *
-                 line_id.price_unit for line_id in order_id.order_line])
+                [order_id.pricelist_id.currency_id.round(line_id.product_uom_qty *
+                 line_id.price_unit) for line_id in order_id.order_line])
 
     discount_method = fields.Selection(
         [('fixed', 'Fixed'), ('per', 'Percentage')], string="Discount Method")