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
for move in self:
            # 
            if move.move_orig_ids:
                move_waiting |= move
            else:
                if move.procure_method == 'make_to_order':
                    move_create_proc |= move
                else:
                    move_to_confirm |= move
            if not move.picking_id and move.picking_type_id:
                key = (move.group_id.id, move.location_id.id, move.location_dest_id.id)
                if key not in to_assign:
                    to_assign[key] = self.env['stock.move']
                to_assign[key] |= move
        # 
        for move in move_create_proc:
            values = move._prepare_procurement_values()
            origin = (move.group_id and move.group_id.name or (move.rule_id and move.rule_id.name or move.origin or move.picking_id.name or "/"))
            self.env['procurement.group'].run(move.product_id, move.product_uom_qty, move.product_uom, move.location_id, move.rule_id and move.rule_id.name or "/", origin,
                                              values)
        move_to_confirm.write({'state': 'confirmed'})
        (move_waiting | move_create_proc).write({'state': 'waiting'})
        # 
        for moves in to_assign.values():
            moves._assign_picking()
        self._push_apply()
        if merge:
            return self._merge_moves(merge_into=merge_into)
        return self
    def _prepare_procurement_values(self):