Category list "Top display (large)" doesn't look right when there are 3 columns

My site’s home page prominently shows categories as with “Top display (large)”. However, in some screen widths the categories don’t look right:
* 4-category wide – looks great (though I wish the bottom 2 where centered)
* 2-category wide – looks great
* 3-category wide (for example, portrait-mode iPad) – looks wrong: first line has 3 categories, second has only 1 category, and last has 3 again.

Looking in the resulting code, looks like the code produces 4-category rows, which the browser is unable to reflow when there’s only room for 3 categories. If the code produces a single row, the browser would be more free the reflow.