You may need to recheck your typing, or your initial value.

To be accurate you should use 1/96 instead of 0.010417, as the latter has
some rounding errors from the true value of 0.0104166666666... (with the
6s continuing to infinity)

Or, instead of having to calculate divisors, you can let Excel do all the
work...

=MROUND(A1,TIME(0,15,0))

Rick