This rule has its formal name, called "round to even".

Sorry, I didn't notice that bmann already mentioned this term in his post ;-)

To support what bmann said below, I tried this c code, regardless whether I define i as float or double, the round to even rule does apply. The c compiler I used is borland c 5.5, my PC is windows XP.

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char * * argv) {
    for (double i=0; i < 10; i += .5) {
            printf("%.1f: %.0f\n", i, i);
    }
    return 0;    
}
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