Superscale resolution?

What is the easiest way to superscale the resolution? What I want is to render 1.2x or 1.5x the number of pixels on the screen, then downscale to the actual screen resolution. Basically, I've maxed out the antialiasing settings, and I'm still getting aliasing on some textures and I think this is the only solution. This will only ever be run on my PC, it does not need to dynamically adapt to the capability of different machines. It will be viewed on the HTC Vive, that might make a difference. I've used Steam's "The Lab Renderer", but due to incompatability with certain screen space image effects, I don't want to use that here.