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
extra_move = self
        rounding = self.product_uom.rounding
        # 
        if float_compare(self.quantity_done, self.product_uom_qty, precision_rounding=rounding) > 0:
            # 
            extra_move_quantity = float_round(
                self.quantity_done - self.product_uom_qty,
                precision_rounding=self.product_uom.rounding,
                rounding_method ='UP')
            extra_move_vals = self._prepare_extra_move_vals(extra_move_quantity)
            extra_move = self.copy(default=extra_move_vals)
            if extra_move.picking_id:
                extra_move = extra_move._action_confirm(merge_into=self)
            else:
                extra_move = extra_move._action_confirm()
            # 
            if self.exists() and not self.picking_id:
                for move_line in self.move_line_ids.filtered(lambda ml: ml.qty_done):
                    if float_compare(move_line.qty_done, extra_move_quantity, precision_rounding=rounding) <= 0:
                        # 
                        move_line.move_id = extra_move.id
                        extra_move_quantity -= move_line.qty_done
                    else:
                        # 
                        quantity_split = float_round(
                            move_line.qty_done - extra_move_quantity,
                            precision_rounding=self.product_uom.rounding,
                            rounding_method='UP')
                        move_line.qty_done = quantity_split
                        move_line.copy(default={'move_id': extra_move.id, 'qty_done': extra_move_quantity, 'product_uom_qty': 0})