I do agree that honesty is normally the best policy, without wanting to come across as too judgemental, it is not very fair that by lying about your qualifications, it means that you could get the position over someone else who may have put the hard work and effort in to pass their exams honestly.
If you do decide to go down this route because you feel you have no other choice, why don't you start to take the extra qualifications anyway. If you get found out by your
employer, then at least you can show them that you were trying to do something to try to rectify the situation and it may not look as bad to them.
Finally I may be stating the obvious, but if you are successful and get a job this way, my advice would then be as to work hard and make yourself as indispensible as possible. Then there is a chance that if you get found out, they will not want to lose such a hard and reliable worker!