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
product_qty = fields.Float(
        'Real Quantity', compute='_compute_product_qty', inverse='_set_product_qty',
        digits=0, store=True,
        help='Quantity in the default UoM of the product')
    product_uom_qty = fields.Float(
        'Initial Demand',
        digits=dp.get_precision('Product Unit of Measure'),
        default=0.0, required=True, states={'done': [('readonly', True)]},
        help="This is the quantity of products from an inventory "
             "point of view. For moves in the state 'done', this is the "
             "quantity of products that were actually moved. For other "
             "moves, this is the quantity of product that is planned to "
             "be moved. Lowering this quantity does not generate a "
             "backorder. Changing this quantity on assigned moves affects "
             "the product reservation, and should be done with care.")
    product_uom = fields.Many2one('product.uom', 'Unit of Measure', required=True)
    
    product_tmpl_id = fields.Many2one(
        'product.template', 'Product Template',
        related='product_id.product_tmpl_id',
        help="Technical: used in views")
    product_packaging = fields.Many2one(
        'product.packaging', 'Preferred Packaging',
        help="It specifies attributes of packaging like type, quantity of packaging,etc.")
    location_id = fields.Many2one(
        'stock.location', 'Source Location',
        auto_join=True, index=True, required=True,
        help="Sets a location if you produce at a fixed location. This can be a partner location if you subcontract the manufacturing operations.")
    location_dest_id = fields.Many2one(
        'stock.location', 'Destination Location',