Almost every time I take a taxi from Santo Domingo to the SDQ airport and get out, there is an airport employee waiting there on the curb who takes my suitcase and puts it on some conveyor belt where it is scanned or x-rayed or something before I actually enter the airport. The whole process takes about 5 seconds, but the guys seem like they are expecting a tip. Does anyone know what this is about and what kind of tip, if any, is appropriate? Thank you.