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
addons/stock/tests/test_move2.py
lot2 = self.env['stock.production.lot'].create({
            'name': 'lot2',
            'product_id': self.productA.id,
        })
        picking_pick, picking_client = self.create_pick_ship()
        location = self.env['stock.location'].browse(self.stock_location)
        
        self.env['stock.quant']._update_available_quantity(self.productA, location, 10.0)
        picking_pick.action_as()
        picking_pick.move_lines[0].move_line_ids[0].write({
            'qty_done': 10.0,
            'lot_id': lot1.id,
        })
        picking_pick.action_done()
        self.assertEqual(picking_pick.state, 'done', 'The state of the pick should be done')
        self.assertEqual(picking_client.state, 'ased', 'The state of the client should be ased')
        self.assertEqual(picking_pick.move_lines.quantity_done, 10.0, 'Wrong quantity_done for pick move')
        self.assertEqual(picking_client.move_lines.product_qty, 10.0, 'Wrong initial demand for client move')
        self.assertEqual(picking_client.move_lines.move_line_ids.lot_id, lot1, 'Wrong lot for client move line')
        self.assertEqual(picking_client.move_lines.reserved_availability, 10.0, 'Wrong quantity already reserved for client move')
        picking_pick.move_lines[0].move_line_ids[0].lot_id = lot2.id
        self.assertEqual(picking_pick.state, 'done', 'The state of the pick should be done')
        self.assertEqual(picking_client.state, 'ased', 'The state of the client should be partially available')
        self.assertEqual(picking_pick.move_lines.quantity_done, 10.0, 'Wrong quantity_done for pick move')
        self.assertEqual(picking_client.move_lines.product_qty, 10.0, 'Wrong initial demand for client move')
        self.assertEqual(picking_client.move_lines.move_line_ids.lot_id, lot2, 'Wrong lot for client move line')
        self.assertEqual(picking_client.move_lines.reserved_availability, 10.0, 'Wrong quantity already reserved for client move')
        # 
        picking_client.action_as()
    def test_chained_move_with_uom(self):