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
domain = [('location_from_id', '=', move.location_dest_id.id)]
            
            routes = move.product_id.route_ids | move.product_id.categ_id.total_route_ids
            rules = Push.search(domain + [('route_id', 'in', routes.ids)], order='route_sequence, sequence', limit=1)
            if not rules:
                
                
                if move.warehouse_id:
                    rules = Push.search(domain + [('route_id', 'in', move.warehouse_id.route_ids.ids)], order='route_sequence, sequence', limit=1)
                elif move.picking_id.picking_type_id.warehouse_id:
                    rules = Push.search(domain + [('route_id', 'in', move.picking_id.picking_type_id.warehouse_id.route_ids.ids)], order='route_sequence, sequence', limit=1)
            
            if rules and (not move.origin_returned_move_id or move.origin_returned_move_id.location_dest_id.id != rules.location_dest_id.id):
                rules._apply(move)
    def _merge_moves_fields(self):
        """ This method will return a dict of stock move’s values that represent the values of all moves in `self` merged. """
        state = self._get_relevant_state_among_moves()
        origin = '/'.join(set(self.filtered(lambda m: m.origin).mapped('origin')))
        return {
            'product_uom_qty': sum(self.mapped('product_uom_qty')),
            'date': min(self.mapped('date')),
            'date_expected': min(self.mapped('date_expected')) if self.mapped('picking_id').move_type == 'direct' else max(self.mapped('date_expected')),
            'move_dest_ids': [(4, m.id) for m in self.mapped('move_dest_ids')],
            'move_orig_ids': [(4, m.id) for m in self.mapped('move_orig_ids')],
            'state': state,
            'origin': origin,
        }
    @api.model
    def _prepare_merge_moves_distinct_fields(self):