learn how to unsharp mask
it's really not very hard, and you can get software that does it for free. also, like people have said, for ordinary macro work, F/8-11 is often sharper, and gives you enough DoF.
unsharp masking can't make bad photos good, but it really improves sharpness. spend 5 minutes reading a tutorial online, then download GIMP, or something like that and try it. it really is good.