If you don't care which number is on top as long as they're all the same, it doesn't matter wat number is thrown on die 1 so it has a probability of 1.
For the four subsequent dice the probability is 1 in 6 that they have the same number as die one. So the overall probability is;
1 x 1/6 x 1/6 x 1/6 x 1/6 = 1/1296
Thanks guys but im a bit confused now, is it 7776 to 1 , or 1296 to 1?
Its immaterial what the number is as long as all 5 dice have the same number. (and all 5 dice thrown at the same time)
1296 to 1 if it doesn't matter which number is on the first die, as Calibax has so ably pointed out. However, if you were to ask the odds on throwing, say five sixes, then it would be 7776 yo 1.
Probability is often used incorrectly. To take a crude example, the odds of you winning the lottery is 50-50 (i.e. there are only two states, you win or you don't).
Using this construction, the odds of throwing five dice the same are 1/2 !