break is like drawing the "Go To Jail" card in Monopoly--you "go directly to jail, do not pass GO, do not collect $200". Here when you get to the conditional and it is satisfied, then the code immediately goes to the next line of code after the terminating end of the for loop and so the other code isn't executed that last iteration--the loop did do five iterations here because it took until then for x(n) to be >=5; just that you didn't do anything at all in the loop other than the test.
Perhaps your expectations could be met simply by reordering:
disp('how many iteration done now');
if x(n)>= 5, break, end
Then again, that assumes that what happens now is what you want to happen for the loop for all iterations that it does do...