My guess is the sharpness adjustment in the camera is applied after before the image is compressed and converted to JPEG. Otherwise the individual pixel values would have to be extracted from the compressed JPEG data, sharpness applied, and then the image recompressed into JPEG format. It would be much more efficient and quicker to apply sharpening before compression.
Have you considered capturing the images in RAW (.cr2) as well as JPEG (.jpg) format? You could then process the images in the DPP software which came with the camera. DPP includes the ability to change or modify the "Picture Style".