Fixed #119 -- Explicitly set decimal rounding mode

src/pretix/base/decimal.py

@@ -0,0 +1,5 @@
+from decimal import ROUND_HALF_UP, Decimal
+
+
+def round_decimal(dec):
+    return Decimal(dec).quantize(Decimal('0.01'), ROUND_HALF_UP)

src/pretix/base/payment.py

@@ -11,6 +11,7 @@ from django.template.loader import get_template
 from django.utils.translation import ugettext_lazy as _
 from typing import Any, Dict
 
+from pretix.base.decimal import round_decimal
 from pretix.base.models import CartPosition, Event, Order, Quota
 from pretix.base.settings import SettingsSandbox
 from pretix.base.signals import register_payment_providers
@@ -47,7 +48,7 @@ class BasePaymentProvider:
         """
         fee_abs = self.settings.get('_fee_abs', as_type=Decimal, default=0)
         fee_percent = self.settings.get('_fee_percent', as_type=Decimal, default=0)
-        return (price * fee_percent / 100).quantize(Decimal('.01')) + fee_abs
+        return round_decimal(price * fee_percent / 100) + fee_abs
 
     @property
     def verbose_name(self) -> str:

src/pretix/plugins/banktransfer/hbci.py

@@ -3,6 +3,8 @@ import tempfile
 import time
 from decimal import Decimal
 
+from pretix.base.decimal import round_decimal
+
 
 def hbci_transactions(event, conf):
     try:
@@ -92,7 +94,7 @@ def hbci_transactions(event, conf):
                     num = int(parts[0])
                     denom = int(parts[1])
                     value = Decimal(num) / Decimal(denom)
-                    value = str(value.quantize(Decimal('.01')))
+                    value = str(round_decimal(value))
                 data.append({
                     'payer': "\n".join(payer),
                     'reference': trans.find('purpose').find('value').text,

src/pretix/plugins/banktransfer/mt940import.py

@@ -1,8 +1,9 @@
 import io
-from decimal import Decimal
 
 import mt940
 
+from pretix.base.decimal import round_decimal
+
 
 def parse(file):
     data = file.read()
@@ -20,7 +21,7 @@ def parse(file):
             'reference': "\n".join([
                 t.data.get(f) for f in ('transaction_details', 'customer_reference', 'bank_reference',
                                         'extra_details') if t.data.get(f, '')]),
-            'amount': str(t.data['amount'].amount.quantize(Decimal('.01'))),
+            'amount': str(round_decimal(t.data['amount'].amount)),
             'date': t.data['date'].isoformat()
         })
     return result