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
"""
        Create an invoice line. The quantity to invoice can be positive (invoice) or negative
        (refund).
        :param invoice_id: integer
        :param qty: float quantity to invoice
        """
        precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
        for line in self:
            if not float_is_zero(qty, precision_digits=precision):
                vals = line._prepare_invoice_line(qty=qty)
                vals.update({'invoice_id': invoice_id, 'sale_line_ids': [(6, 0, [line.id])]})
                self.env['account.invoice.line'].create(vals)
    @api.multi
    @api.onchange('product_id')
    def product_id_change(self):