I had thought that there was but it turns out I was just mistaken in the object hierarchy. InlineModelAdmin inherits from BaseModelAdmin the same as ModelAdmin -- I was thinking that InlineModelAdmin inherited from ModelAdmin.

Therefore, I had to determine a way to accomplish this via some spelunking through the code. At first, I thought I'd just create my own template by inheriting or copying the tabular.html template. After looking at it, I determined that I didn't want to figure out how to do a regroup on inline_admin_formset or if even that was the proper way to try to order things in that template.

After a few minutes in the code I realized that I could just subclass BaseInlineFormset and specify the fields that I wanted to order by (in this example I will use start_time and end_time:

from django.contrib import admin
from django.newforms.models import BaseInlineFormset

class MyOrderedFormset(BaseInlineFormset):
    def get_queryset(self):
        qs = super(SessionInlineFormset, self).get_queryset()
        return qs.order_by('start_time', 'end_time')

class MyOrderedInline(admin.TabularInline):
    model = MyModel
    extra = 1
    formset = MyOrderedFormset

That's it. Now after that section of inlines are ordered by start_time and end_time.