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
defaults = self.with_context(force_split_uom_id=self.product_id.uom_id.id)._prepare_move_split_vals(qty)
        if restrict_partner_id:
            defaults['restrict_partner_id'] = restrict_partner_id
        # 
        if self.env.context.get('source_location_id'):
            defaults['location_id'] = self.env.context['source_location_id']
        new_move = self.with_context(rounding_method='HALF-UP').copy(defaults)
        
        # 
        # 
        # 
        new_product_qty = self.product_id.uom_id._compute_quantity(self.product_qty - qty, self.product_uom, round=False)
        new_product_qty = float_round(new_product_qty, precision_digits=self.env['decimal.precision'].precision_get('Product Unit of Measure'))
        self.with_context(do_not_propagate=True, do_not_unreserve=True, rounding_method='HALF-UP').write({'product_uom_qty': new_product_qty})
        new_move = new_move._action_confirm(merge=False)
        return new_move.id
    def _recompute_state(self):
        for move in self:
            if move.reserved_availability == move.product_uom_qty:
                move.state = 'assigned'
            elif move.reserved_availability and move.reserved_availability <= move.product_uom_qty:
                move.state = 'partially_available'
            else:
                if move.procure_method == 'make_to_order' and not move.move_orig_ids:
                    move.state = 'waiting'
                elif move.move_orig_ids and not all(orig.state in ('done', 'cancel') for orig in move.move_orig_ids):
                    move.state = 'waiting'
                else:
                    move.state = 'confirmed'