[FIX] account: dashboard graphs proper float rounding

Steps to reproduce:
- install accounting
- go to the accounting main view and hover some of the graphs

Previous behavior:
rounding was inconsistent and would lead to weird js floats
like 65.00000000000001

Current behavior:
floats are rounded to 2 digits after

opw-2172686

closes odoo/odoo#45336

X-original-commit: c00f4962eb790787fffef99595ac14dbef026055
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/account/models/account_journal_dashboard.py

@@ -84,6 +84,7 @@ class account_journal(models.Model):
     # Below method is used to get data of bank and cash statemens
     def get_line_graph_datas(self):
         """Computes the data used to display the graph for bank and cash journals in the accounting dashboard"""
+        currency = self.currency_id or self.company_id.currency_id
 
         def build_graph_data(date, amount):
             #display date in locale format
@@ -123,7 +124,7 @@ class account_journal(models.Model):
             date = val['date']
             if date != today.strftime(DF):  # make sure the last point in the graph is today
                 data[:0] = [build_graph_data(date, amount)]
-            amount -= val['amount']
+            amount = currency.round(amount - val['amount'])
 
         # make sure the graph starts 1 month ago
         if date.strftime(DF) != last_month.strftime(DF):