It's not ok to add that fee in.
If you add it in, you're liable to price yourself right into having to re-list your item for less money later on. UNLESS, you can add the fee into the shipping & keep it reasonably priced to sell, I'd leave the fee out.
I sell on ebay often enough to avoid this fee. I price my items affordably so people will be interested in buying and/or bidding on them. My time to the post office to ship it is MY own problem. I knew this going into selling ahead of time on ebay. The money I make on ebay is for extra groceries or to help pay a bill. When I go to the post office to ship items that I've sold, I'm already going out for other errands. If you can't afford the trips to the post office, UPS or FedEx, then you shouldn't bother selling on ebay.
I'd avoid buying an ebay item from you, knowing you've added that fee in. Guess what...I'll tell tons of people about your ebay id & word will spread that you're adding fees in that aren't necessary. Your items won't sell after awhile, too. Think I'm kidding? I'm not. This has happened to several people I know who've thought it was ok to add in this handling fee you want to add into your price. They lost loyal customers & potential customers by word of mouth when word got out they were adding in fees to their list prices and/or bids. They've since removed this added fee & are back to being Power Sellers on ebay.
Edit on 09-23-08:
If you didn't want someone disagreeing with you, you had no business asking a question on here.
I don't need to know your ebay id to not buy from you. It's sellers like you who damage themselves over time. For every item placed that I want to bid on that is obviously inflated or that I suspect is inflated, I send an email to the seller to ask if they've added fees such as the ones you mention wanting to add. Some are truthful & admit to adding these fees in. Some lie & say they don't when it's blantantly obvious that they have added in additional fees. Those are the ones I pass by & buy that same item from another seller who's more honest. Can the honest ones be lying too? Sure they can. They're reputation in the feedback tells a lot too.
I know people who've been selling on ebay as Power Sellers since it started. I know some of them have had to add these handling fees in to keep afloat. Like I stated above, some have had to remove it to keep afloat.
It all comes down to how much money you're willing to charge people for an item they can find with another seller for less money either on ebay or another site altogether.
So, go ahead, charge your fees. Reap the rewards if you can sell the item(s). When your items have to be relisted because no one bids on them, then you'll realize those handling fees are not worth it in the long run.