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
'quantity_done': 10,
                'state': 'ased',
                'product_uom': self.productA.uom_id.id,
                'picking_id': delivery.id,
                'location_id': self.stock_location,
                'location_dest_id': self.customer_location,
            })]
        })
        delivery.action_done()
        self.assertEqual(len(delivery.move_lines), 2, 'Move should not be merged together')
        for move in delivery.move_lines:
            self.assertEqual(move.quantity_done, move.product_uom_qty, 'Initial demand should be equals to quantity done')
    def test_recheck_availability_1(self):
        """ Check the good behavior of check availability. I create a DO for 2 unit with
        only one in stock. After the first check availability, I should have 1 reserved
        product with one move line. After adding a second unit in stock and recheck availability.
        The DO should have 2 reserved unit, be in available state and have only one move line.
        """
        self.env['stock.quant']._update_available_quantity(self.productA, self.env['stock.location'].browse(self.stock_location), 1.0)
        delivery_order = self.env['stock.picking'].create({
            'location_id': self.stock_location,
            'location_dest_id': self.customer_location,
            'partner_id': self.partner_delta_id,
            'picking_type_id': self.picking_type_out,
        })
        move1 = self.MoveObj.create({
            'name': self.productA.name,
            'product_id': self.productA.id,
            'product_uom_qty': 2,
            'product_uom': self.productA.uom_id.id,