If you are using a 5.2 mp digital camera, I cannot see why you cannot take decent photos. Here is a good tip: take a pen or something, and let the coin lie on it. Let some light shine on it, a table lamp will do very well and get your camera out. You should check out the features before taking pictures. One of the most important features is the "flower" feature, which appears on most modern digital cameras. Press that. Before you press the button fully, gently press the button HALFWAY, so that you allow the camera to focus. If that appears clearly on your screen, then you are doing good. And that is where you should press the button fully.
Note: you should not go TOO close to the coin as cameras usually have some sort of minimum range to be fully optimized.
As for picture cropping, you should get a software called irfanview, homepage should be http://www.irfanview.com
. The software is FREE. It takes a bit of time to fool around, but it is very user friendly.
Hopefully those tips are useful to you.