Impacted versions:

[9.0]
Tested in runbot http://174550-9-0-10dcec.runbot10.odoo.com/

Steps to reproduce:

Set the Tax Calculation Rounding Method to "Round Globally" 
Create a Sales Order with the following lines with 7% taxes

1) 5,095.20 
2) 523.20 
3) 80.64 
4) 54.12 
5) 182.00 
6) 186.20 
![image](https://cloud.githubusercontent.com/assets/16055718/19144073/309aa082-8bda-11e6-81d0-2461c4e9a467.png)

Create a Sales Invoice with the same lines with 7% taxes
![image](https://cloud.githubusercontent.com/assets/16055718/19144078/38048b58-8bda-11e6-9c2b-4b501cfa1e12.png)

Current behavior:

The total taxes in Sales Order are $477.48 

The total taxes in Sales Invoice are $477.50 

Expected behavior:

Both the total taxes in Sales Order and Sales Invoice should be 477.50 

Video/Screenshot link (optional):

moves = self.env['stock.move']
        done = self.env['stock.move'].browse()
        for line in self:
            price_unit = line._get_stock_move_price_unit()
            template = {
                'name': line.name or '',
                'product_id': line.product_id.id,
                'product_uom': line.product_uom.id,
                'date': line.order_id.date_order,
                'date_expected': line.date_planned,
                'location_id': line.order_id.partner_id.property_stock_supplier.id,
                'location_dest_id': line.order_id._get_destination_location(),
                'picking_id': picking.id,
                'partner_id': line.order_id.dest_address_id.id,
                'move_dest_id': False,
                'state': 'draft',
                'purchase_line_id': line.id,
                'company_id': line.order_id.company_id.id,
                'price_unit': price_unit,
                'picking_type_id': line.order_id.picking_type_id.id,
                'group_id': line.order_id.group_id.id,
                'procurement_id': False,
                'origin': line.order_id.name,
                'route_ids': line.order_id.picking_type_id.warehouse_id and [(6, 0, [x.id for x in line.order_id.picking_type_id.warehouse_id.route_ids])] or [],