I'm not sure if the issue will still be present, but when you use certain zoom values in Photoshop, the image is not aliased anymore. When I want a clear picture I use the ALT CTRL and plus minus from numpad for zoom, and not the mouse wheel.
100%, 50%, 25% would behave more like a 1:1 scaling. And maybe also 75%, 66.67%, 33.33%. These values will be automatically used if you use those keyboard shortcuts.