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
if self.env.context.get('default_picking_id'):
            return self.env['stock.picking'].browse(self.env.context['default_picking_id']).group_id.id
        return False
    name = fields.Char('Description', index=True, required=True)
    sequence = fields.Integer('Sequence', default=10)
    priority = fields.Selection(PROCUREMENT_PRIORITIES, 'Priority', default='1')
    create_date = fields.Datetime('Creation Date', index=True, readonly=True)
    date = fields.Datetime(
        'Date', default=fields.Datetime.now, index=True, required=True,
        states={'done': [('readonly', True)]},
        help="Move date: scheduled date until move is done, then date of actual move processing")
    company_id = fields.Many2one(
        'res.company', 'Company',
        default=lambda self: self.env['res.company']._company_default_get('stock.move'),
        index=True, required=True)
    date_expected = fields.Datetime(
        'Expected Date', default=fields.Datetime.now, index=True, required=True,
        states={'done': [('readonly', True)]},
        help="Scheduled date for the processing of this move")
    product_id = fields.Many2one(
        'product.product', 'Product',
        domain=[('type', 'in', ['product', 'consu'])], index=True, required=True,
        states={'done': [('readonly', True)]})
    ordered_qty = fields.Float('Ordered Quantity', digits=dp.get_precision('Product Unit of Measure'))