Best lens to use with a Nikon D70 for coin photography

If y'all can drag yourselves away from the Nikon vs. Canon debate long enough, could I get an answer to this photography question?
I shoot with a Nikon D70 and I love the camera body. I am currently using the Nikkor 18-70mm zoom lens that came with my camera (a graduation gift) and I'm finding that no matter how good I'm able to adjust the focus I can't get the focus as razor sharp as I'd like. I'm also not able to zoom in quite as far as I'd like on some of the smaller denominations. I think my issue with focus is due to the lens being a zoom lens (I'm shooting on manual focus since autofocus is no good at such close range). Obviously, the inability to photograph smaller coins is also lens-related.
Can anyone shooting with a nikon give me a full-size example shot (cropped, obviously) and tell me about the lens you're using and whether you like it? Thanks!
I'm attaching my best shot thus far to illustrate the soft focus issue I've got.
I shoot with a Nikon D70 and I love the camera body. I am currently using the Nikkor 18-70mm zoom lens that came with my camera (a graduation gift) and I'm finding that no matter how good I'm able to adjust the focus I can't get the focus as razor sharp as I'd like. I'm also not able to zoom in quite as far as I'd like on some of the smaller denominations. I think my issue with focus is due to the lens being a zoom lens (I'm shooting on manual focus since autofocus is no good at such close range). Obviously, the inability to photograph smaller coins is also lens-related.
Can anyone shooting with a nikon give me a full-size example shot (cropped, obviously) and tell me about the lens you're using and whether you like it? Thanks!
I'm attaching my best shot thus far to illustrate the soft focus issue I've got.

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President, Racine Numismatic Society 2013-2014; Variety Resource Dimes; See 6/8/12 CDN for my article on Winged Liberty Dimes; Ebay
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<< <i>I think your lighting is more important than the lens. >>
I almost posted that thought myself but one does need at least a macro lens built to focus at these distances and the proper resolving power to create a sharp image (the 18-70 he mentions doesn't - it's a good lens but has no macro). Once the basic lens needs are met, I agree, it comes down to lighting.
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I use a Nikon 65mm micro lens, which I somehow managed to get used on eBay for less than $250. I'm thrilled with it.
An off-brand micro lens would be the next option down the price list.
The screw-in closeup filters would be the cheapest option, but so might the image results.
http://parrishm.myweb.uga.edu/coins/images/photo_setup_01.jpg
John