The problem with jaggies is that they only appear in certain circumstances, and only on some parts of the image - if you use a basic sharpening method, either parts of the pic may display jaggies, or, if you lower the sharpening to avoid these, the pic looks soft.
There are tools like FocalBlade which give you much more control over how your picture is sharpened. Alternatively, you can apply sharpening to particular parts of the picture in varying degrees.
Selective sharpening can be done by masking off parts of the pic you don't want sharpened. But this can be a bit tedious, and its not easy to know which parts are going to go jaggy before you sharpen.
My preferred method is to create a duplicate layer (Layers -> duplicate layer) and then apply sharpening to that layer which looks right for the picture overall. If some bits appear jaggy, or oversharp, simply use the eraser tool to remove that part of the duplicate layer, and the unsharpened background layer will show through. You can vary the intensity of the erase tool, so have complete control over how sharpened a particular detail of the image appears.
Once you're happy, just flatten the layers and save as usual.
Colin K. Work, Pixstel