Hi gbill2004,
I would probably choose sheets with a pocket depth that are a little closer to the thickness of your mattress rather than deep pocket sheets because some people find that the sheets can bunch up if the pockets are more than a few inches deeper than the mattress (although it seems to bother some people more than others and it will also depend on the specifics of the mattress and the sheets so there is no “exact” answer). A pocket depth that is about 1" to 3" more than your mattress (so that there is some room for the sheets to tuck under the mattress) would be ideal but If your sheets are designed to fit a mattress up to 14" or 15" thick then for most people they would be fine on a 10" mattress although shallower pockets will fit more snugly. Sheets that have a strong elastic all the way around the perimeter will be less likely to fit loosely or bunch up if they are a little deeper than they need to be than sheets that only have elastic around the corners.
There is also much more information about choosing sheets in post #7 here along with the other posts, topics, and sources of information that it links to.
Phoenix