I have to add my two cents here...
Your best bet is to remove all the tea bags from the box, and seal in a ziplock plastic bag. Unassemble the box, leaving it flat but able to re-assemble at the other end. Place this into a Jiffy envelope. Fill out one of those green Declaraitions stickers, available at the post office, fill in your name, tick the 'gift' option, in description write 'teabags from home!' and put a value of maybe $5 in...
Its cheaper to send an envelope than a parcel which would be what the fully assembled box would be, including the box shows that they are genuine tea bags, and filling in a declairation just makes everything a lot easier.