Please Help: As 11 accounting of US$ accounts in india

Professional friends i have opened us$ accounts in india and i received us$ against export and i utilise that dollar against import so i have t convert this dollar in idian ruppeess so guide me on that issue because i am maintaining my books of accounts in indian rupees so please guide me to which exchange rate i should take for conversion that dollar so i can settled my foreign creditors and debtors.