The import of foreign currency is free. If the amount of foreign currency is equal to or greater than the equivalent of 25,000 Tunisian dinars you are required to declare it to Customs at the airport. 

If you are a non-resident and intend to re-export a balance of foreign currencies equal to or greater than the equivalent of 5,000 Tunisian dinars, you are required to declare it to Customs. The currency declaration must be made on the "Foreign Currency Import Declaration" form before leaving the zone under Customs.