Jimbo,
Given your budget and the fact that you don't really want to upgrade to a DSLR, I would probably recommend: Canon PowerShot A720 IS. It is highly rated for Macro shots and got a good review from several photo raters.
BTW: Check out Dpreview below for many side-by-side features and camera comparisons.
http://http://www.dpreview.com/reviews/canona720is/
However, having said that. If you're looking to improve your photography for items like jewelry, your most important element will be lighting. I'd recommend investing in a pair of cheap table lamps and a soft-box similar to what is pictured below (alternatively you can make one from a cardboard box and some fabric).
