Use non-monospace centering for centis in the 10-19 range when the timer is not running.

[lgarron]

When the timer is running, we should use monospace to keep the "digital display" effect.

But when the timer stops and the centiseconds are in the 10s, we get an ugly misalignment:

We should use non-monospace centering for the initial digit (similar to how we do it for seconds).
The implementation should be shared with the code for seconds.