My employer has tried to shortchange me before several times. At times in excess of $50 per fortnight.
I confronted them about it and it has never happened to me since. I also keep a record of my hours to make sure that my pay is correct.
Told my co-workers to keep an eye out, but I'm not sure how much money they've already lost.
Sure, the employer saves money by sometimes shortchanging staff but when they're caught... is it really worth the 'profit'?