As former Ebayer, or Ebay partner.
Its not the worst thing in the world to go one or two dollers over, depending on the item, it may take more or less packaging to transport, and the few dollars you can reinburse yourself for the pakaging costs. To low isnt always good, the only tip I can give Is to price your postage at a rate your comfateble with, I know you are trying to sell your product or item to customers, but you dont want to comfort them so much that you end up loosing.
Research posatge costs, online or go to your local office for a price list. Weigh your item of the Total weight of the packaging and inner padding, and the item. do this for different postage methods and list your item. Traders such as me dont really care about the one or two dollers over, and some times such as my recent Micron Figure, I paid 27 dollers postage to the UK from singapore or something due to I desprately wanted the figure.
In other words as long as you have smartly and neatly packed you item in a sturdy container, im sure the reciever wont mind the extra few dollers if it gets there in good condition, if they complain try uping your prices for the better packaging and better transport.
Thats my tip, not the best in the world, but hopefully it should help, even that little bit if not
Good luck with the Ebaying, and who knows I may purchase something from you in the future.