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/models/stock_move.py
if any(move.state == 'done' for move in self):
            raise UserError(_('You cannot cancel a stock move that has been set to \'Done\'.'))
        for move in self:
            if move.state == 'cancel':
                continue
            move._do_unreserve()
            siblings_states = (move.move_dest_ids.mapped('move_orig_ids') - move).mapped('state')
            if move.propagate:
                # 
                if all(state == 'cancel' for state in siblings_states):
                    move.move_dest_ids._action_cancel()
            else:
                if all(state in ('done', 'cancel') for state in siblings_states):
                    move.move_dest_ids.write({'procure_method': 'make_to_stock'})
                    move.move_dest_ids.write({'move_orig_ids': [(3, move.id, 0)]})
        self.write({'state': 'cancel', 'move_orig_ids': [(5, 0, 0)]})
        return True
    def _prepare_extra_move_vals(self, qty):