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):

'''
        This function returns an action that display existing picking orders of given purchase order ids.
        When only one found, show the picking immediately.
        '''
        action = self.env.ref('stock.action_picking_tree')
        result = action.read()[0]
        
        result['context'] = {}
        pick_ids = sum([order.picking_ids.ids for order in self], [])
        
        if len(pick_ids) > 1:
            result['domain'] = "[('id','in',[" + ','.join(map(str, pick_ids)) + "])]"
        elif len(pick_ids) == 1:
            res = self.env.ref('stock.view_picking_form', False)
            result['views'] = [(res and res.id or False, 'form')]
            result['res_id'] = pick_ids and pick_ids[0] or False
        return result
    @api.multi
    def action_view_invoice(self):