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
owner_id =reserved_quant.owner_id.id or False,
            )
        return vals
    def _update_reserved_quantity(self, need, available_quantity, location_id, lot_id=None, package_id=None, owner_id=None, strict=True):
        """ Create or update move lines.
        """
        self.ensure_one()
        if not lot_id:
            lot_id = self.env['stock.production.lot']
        if not package_id:
            package_id = self.env['stock.quant.package']
        if not owner_id:
            owner_id = self.env['res.partner']
        taken_quantity = min(available_quantity, need)
        # 
        # 
        # 
        # 
        # 
        # 
        taken_quantity_move_uom = self.product_id.uom_id._compute_quantity(taken_quantity, self.product_uom, rounding_method='DOWN')
        taken_quantity = self.product_uom._compute_quantity(taken_quantity_move_uom, self.product_id.uom_id, rounding_method='HALF-UP')
        quants = []
        try:
            if not float_is_zero(taken_quantity, precision_rounding=self.product_id.uom_id.rounding):
                quants = self.env['stock.quant']._update_reserved_quantity(
                    self.product_id, location_id, taken_quantity, lot_id=lot_id,
                    package_id=package_id, owner_id=owner_id, strict=strict
                )
        except UserError: