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):

for order in self:
            email_act = order.action_quotation_send()
            if email_act and email_act.get('context'):
                email_ctx = email_act['context']
                email_ctx.update(default_email_from=order.company_id.email)
                order.with_context(email_ctx).message_post_with_template(email_ctx.get('default_template_id'))
        return True
    @api.multi
    def action_done(self):
        self.write({'state': 'done'})
    @api.model
    def _prepare_procurement_group(self):
        return {'name': self.name}
    @api.multi
    def action_confirm(self):
        for order in self:
            order.state = 'sale'
            if self.env.context.get('send_email'):
                self.force_quotation_send()
            order.order_line._action_procurement_create()
            if not order.project_id:
                for line in order.order_line:
                    if line.product_id.invoice_policy == 'cost':
                        order._create_analytic_account()
                        break
        if self.env['ir.values'].get_default('sale.config.settings', 'auto_done_setting'):
            self.action_done()
        return True
    @api.multi
    def _create_analytic_account(self, prefix=None):