The OP came back and confirmed snap to grid was off in post #9, so my assumption is zoom level, as John T also mentioned above. There are only so many pixels on the screen, so unless you are zoomed in close enough, a single pixel is representing an average, and potentially thousands of samples.
As an aside, I was doing an experiment from the course I am taking, where a "single sample" was modified in Audactity (creating an audible click). The first thing I did after replicating his "demonstration" was open that in SONAR to look at the samples, and here is that screen shot (the rest of the experiment is immaterial to the OP).
Edit: This is a 1kHz sine wave at 44.1kHz sampling rate.
It took quite a while just to find the damn thing, but I did a lot of
moving of that clip (in fact, it can easily be moved
one sample at a time zoomed in this far).