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):

"""
        Prepare the dict of values to create the new invoice for a sales order. This method may be
        overridden to implement custom invoice generation (making sure to call super() to establish
        a clean extension chain).
        """
        self.ensure_one()
        journal_id = self.env['account.invoice'].default_get(['journal_id'])['journal_id']
        if not journal_id:
            raise UserError(_('Please define an accounting sale journal for this company.'))
        invoice_vals = {
            'name': self.client_order_ref or '',
            'origin': self.name,
            'type': 'out_invoice',
            'account_id': self.partner_invoice_id.property_account_receivable_id.id,
            'partner_id': self.partner_invoice_id.id,
            'journal_id': journal_id,
            'currency_id': self.pricelist_id.currency_id.id,
            'comment': self.note,
            'payment_term_id': self.payment_term_id.id,
            'fiscal_position_id': self.fiscal_position_id.id or self.partner_invoice_id.property_account_position_id.id,
            'company_id': self.company_id.id,
            'user_id': self.user_id and self.user_id.id,
            'team_id': self.team_id.id
        }
        return invoice_vals
    @api.multi
    def print_quotation(self):
        self.filtered(lambda s: s.state == 'draft').write({'state': 'sent'})
        return self.env['report'].get_action(self, 'sale.report_saleorder')