Fix floating point inaccuracy in edge cases, behavior not consistent

Inaccuracy in Math functions may cause ie. Tweens not to get to the end values properly if using cos/sin based Easings. Especially it happens that Math.cos( 1 * Math.PI / 2) != 0 on Desktop Chrome OSX, but on Android Chrome result is correct. Possibly difference in floating point accuracy and Math.PI approx value.