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):

return False
    @api.multi
    def button_dummy(self):
        return True
    @api.multi
    def unlink(self):
        for order in self:
            if order.state != 'draft':
                raise UserError(_('You can only delete draft quotations!'))
        return super(SaleOrder, self).unlink()
    @api.multi
    def _track_subtype(self, init_values):
        self.ensure_one()
        if 'state' in init_values and self.state == 'sale':
            return 'sale.mt_order_confirmed'
        elif 'state' in init_values and self.state == 'sent':
            return 'sale.mt_order_sent'
        return super(SaleOrder, self)._track_subtype(init_values)
    @api.multi
    @api.onchange('partner_shipping_id', 'partner_id')
    def onchange_partner_shipping_id(self):