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):

"""
        Compute the invoice status of a SO line. Possible statuses:
        - no: if the SO is not in status 'sale' or 'done', we consider that there is nothing to
          invoice. This is also hte default value if the conditions of no other status is met.
        - to invoice: we refer to the quantity to invoice of the line. Refer to method
          `_get_to_invoice_qty()` for more information on how this quantity is calculated.
        - upselling: this is possible only for a product invoiced on ordered quantities for which
          we delivered more than expected. The could arise if, for example, a project took more
          time than expected but we decided not to invoice the extra cost to the client. This
          occurs onyl in state 'sale', so that when a SO is set to done, the upselling opportunity
          is removed from the list.
        - invoiced: the quantity invoiced is larger or equal to the quantity ordered.
        """
        precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
        for line in self:
            if line.state not in ('sale', 'done'):
                line.invoice_status = 'no'
            elif not float_is_zero(line.qty_to_invoice, precision_digits=precision):
                line.invoice_status = 'to invoice'
            elif line.state == 'sale' and line.product_id.invoice_policy == 'order' and\
                    float_compare(line.qty_delivered, line.product_uom_qty, precision_digits=precision) == 1:
                line.invoice_status = 'upselling'
            elif float_compare(line.qty_invoiced, line.product_uom_qty, precision_digits=precision) >= 0:
                line.invoice_status = 'invoiced'
            else:
                line.invoice_status = 'no'
    @api.depends('product_uom_qty', 'discount', 'price_unit', 'tax_id')
    def _compute_amount(self):