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):

addons/sale/sale.py
for line in self:
            line.price_reduce = line.price_subtotal / line.product_uom_qty if line.product_uom_qty else 0.0
    @api.multi
    def _compute_tax_id(self):
        for line in self:
            fpos = line.order_id.fiscal_position_id or line.order_id.partner_id.property_account_position_id
            
            taxes = line.product_id.taxes_id.filtered(lambda r: not line.company_id or r.company_id == line.company_id)
            line.tax_id = fpos.map_tax(taxes) if fpos else taxes
    @api.multi
    def _prepare_order_line_procurement(self, group_id=False):
        self.ensure_one()
        return {
            'name': self.name,
            'origin': self.order_id.name,
            'date_planned': datetime.strptime(self.order_id.date_order, DEFAULT_SERVER_DATETIME_FORMAT) + timedelta(days=self.customer_lead),
            'product_id': self.product_id.id,
            'product_qty': self.product_uom_qty,
            'product_uom': self.product_uom.id,
            'company_id': self.order_id.company_id.id,
            'group_id': group_id,
            'sale_line_id': self.id
        }
    @api.multi
    def _action_procurement_create(self):