https://github.com/odoo/odoo/blob/b192431aeecc59b48898ce9c6f276b82d65cbfa6/addons/stock/models/stock_move.py#L1026

rounding_method ='UP'
I think it **need be changed to:**
rounding_method ='HALF-UP'

I get this message then I Verify new Delivery(stock.picking):

> The initial demand has been updated.
> My Product
> Quantity : 5.951 -> 5.949999999999999 

and
> The initial demand has been updated.
> My Product
> Quantity : 5.951 -> 5.951 


How I did it(you can also repeat this error): Create new Product > add Qty on hand > Create SO > Add Product with quantity 5.5 > Verify > open Delivery > add Delivered qty 5.95 > Verify > Get trouble: odoo change my qty to 5.951
![default](https://user-images.githubusercontent.com/34191760/39213952-9b246470-481b-11e8-8e06-a074b1044536.png)

You can try execute in python:
5.95 - 5.5 = 0.4500000000000002

Look at the code:
```
            extra_move_quantity = float_round(
                self.quantity_done - self.product_uom_qty,
                precision_rounding=self.product_uom.rounding,
                rounding_method ='UP')
```
if you setup parameters like this:
```
            0.451 = float_round(
                5.95 - 5.5,
                precision_rounding=self.product_uom.rounding,
                rounding_method ='UP')
```
Then you get 0.451.  This is wrong!
Try:
```
            0.45 = float_round(
                5.95 - 5.5,
                precision_rounding=self.product_uom.rounding,
                rounding_method ='HALF-UP')
```
0.45 = 5.95 - 5.5
""" Prepare specific key for moves or other componenets that will be created from a procurement rule
        comming from a stock move. This method could be override in order to add other custom key that could
        be used in move/po creation.
        """
        self.ensure_one()
        group_id = self.group_id or False
        if self.rule_id:
            if self.rule_id.group_propagation_option == 'fixed' and self.rule_id.group_id:
                group_id = self.rule_id.group_id
            elif self.rule_id.group_propagation_option == 'none':
                group_id = False
        return {
            'company_id': self.company_id,
            'date_planned': self.date,
            'move_dest_ids': self,
            'group_id': group_id,
            'route_ids': self.route_ids,
            'warehouse_id': self.warehouse_id or self.picking_id.picking_type_id.warehouse_id or self.picking_type_id.warehouse_id,
            'priority': self.priority,
        }
    def _force_assign(self):
        """ Allow to work on stock move lines even if the reservationis not possible. We just mark
        the move as assigned, so the view does not block the user.
        """
        for move in self.filtered(lambda m: m.state in ['confirmed', 'waiting', 'partially_available', 'assigned']):
            move.write({'state': 'assigned'})
    def _prepare_move_line_vals(self, quantity=None, reserved_quant=None):