I wouldn't bother. First, it might mean something created only @1x image. Offhand - for the sake of economy, to pictures loaded faster. It is clear that the retina will suffer the quality, but the download speed is more critical (of two evils choose the lesser).
Secondly, devices with retina display are increasingly apskeyl. That is, the operating system, graphics card or browser enhances an image with low resolution.
As for the question. The interpolation method and post-processing are highly dependent on the lowest graphics. That is, it is necessary to look and experiment. But if you want simple and not confusing, then photoshop supports automatic interpolation, after which you can apply the sharpness.
Not to say that it's worth it. More precisely, it is probably not worth it.