I never have problem with tic/toc. I believe it inquires CPU frequency/counter or clock and derive time from it. It's very direct and simple.
If you get some strange result, then as Walter said something must trigger a later tic when you are not expected.
It might be also safter using tic/toc with timerVal
t0 = tic();
dt = toc(t0)
if you are not sure about what happens during "..."