Indiana law prohibits carrying firearms in certain places (except by law enforcement officials or security guards) such as school property, school buses, post offices, secure areas of airports, commercial or charter aircraft and riverboats.
There is no provision that prohibits you from carrying a weapon into a bank.
Edit: Unless it is a Federal Bank or any U.S. Government Property.
Indiana law makes no mention of carry at US Post offices. There are contradictory federal laws on carry at the Post office. However it is legal to ship a firearm from a post office.