How to calculate total chance from different simultaneous chances

It's always 5% per hit.
http://en.wikipedia.org/wiki/Gambler's_fallacy

You don't calculate them together, you calculate the two as separate events.
At least that's my understanding of it.

Yes, it's always 5% per hit, however there is a 100% chance that the next result -might- differ from the previous one.

However, that still keeps the chance at 5% .

But, since the random number generator in computers is never truly random, the chance of of the next result being different depends on how the RNG is made.