Make sure total is calculated as a Decimal

src/pretix/presale/checkoutflow.py

@@ -1,3 +1,5 @@
+from decimal import Decimal
+
 from django.conf import settings
 from django.contrib import messages
 from django.core.exceptions import ValidationError
@@ -460,7 +462,7 @@ class PaymentStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
     def _total_order_value(self):
         total = get_cart_total(self.request)
         total += sum([f.value for f in get_fees(self.request.event, self.request, total, self.invoice_address, None)])
-        return total
+        return Decimal(total)
 
     @cached_property
     def provider_forms(self):

src/pretix/presale/views/__init__.py

@@ -1,5 +1,6 @@
 from collections import defaultdict
 from datetime import datetime, timedelta
+from decimal import Decimal
 from functools import wraps
 from itertools import groupby
 
@@ -198,7 +199,7 @@ def get_cart_total(request):
         else:
             request._cart_total_cache = CartPosition.objects.filter(
                 cart_id=get_or_create_cart_id(request), event=request.event
-            ).aggregate(sum=Sum('price'))['sum'] or 0
+            ).aggregate(sum=Sum('price'))['sum'] or Decimal('0.00')
     return request._cart_total_cache