Alright I figured out how to reset specific opening balance values manually. This worked great for me as I was able to edit any account and bring everything back to $0.00 balances without deleting the business profile which I had already created!
1. Find out which accounts are still reporting an open balance (even though you have deleted any applicable invoices) - Reports > Balance Sheet... > View
2. If any of the items listed in this report are showing a balance, note their account number and go to View > Chart of Accounts..
3. Open the account you would like to clear or mofify