Conversions and former bad deeds

I have read that obedience to the five precepts at least guarantees that practitioners will not fall back into the lower worlds (animal world, wandering spirit world, and hell world) when they are reborn after the present life. So I was wondering if the conversion to Buddhism, the taking of refuge and the beginning to follow the five precepts, "cleansed" the old bad deeds, a bit like baptism among Christians? Does a person who has violated the five precepts, for example by killing or stealing at the beginning of his life, and then halfway through his life until his death starts following the five precepts, still go to hell? Is he definitely condemned to be reborn in hell for his offense?