My oven always rounds up. Until the last minute, when it immediately switches from 2 minutes to 59 seconds.

Just round up. The countdown is done as soon as 0 appears (0 doesn't linger for 1 second).

To expand a bit on what others have said:

If you're counting up, round down. If you're counting down, round up. A human expects the count to finish at precisely the moment we get to the last number in the sequence (zero, for counting down). Do a count in your head to see what I mean.

Apple chose a compromise by rounding to nearest, for it to "feel good", but you lose the ability to exactly predict when the timer ends as a human. Typical Apple.

From looking at the bottom of the linked post (which says it was edited, not sure when in relation to your comment), it sounds like they wanted something that worked across arbitrary times split across units (hour/minute/seconds) without having to handle carry-over. I'm not sure I would choose to alter the times themselves over making the math a bit more complex, but the author has obviously thought about this a lot more than me, and it's nice that they at least considered that alternative.