1. As per sec 44AB only if the T.O or gross receipts exceeds Rs. 1 crore during the year tax audit will be applicable. 
2. In your case since the T.O is only Rs. 5 lakhs tax audit will not be applicable. 
Please correct me if the above solution has an alternative view.

Partnership firms involved in profession with gross receipts of more than Rs.50 lakhs must complete a tax audit. Partnership firm involved in doing business must complete tax audit, if sales turnover exceeds Rs.1 crores.

Partnership firms involved in carrying on a specified profession would be required to maintain book of accounts as per Income Tax Act, if gross receipts is more than Rs.1.5 lakhs in all three previous years.

In case a partnership firm is receiving income profession (other than specified profession), book of accounts must be mandatorily maintained if income exceeds Rs.2.5 lakhs in any one of the three years previous year.

In case a partnership is involved in business, then maintenance of books of account is mandatory if total sales turnover or gross receipts exceed Rs.25 lakhs in any one of the three preceding years.