Center Alignment in 'Select All That Apply' Questions

It would be great to have an option to center-align the icons on the last line of a 'Select all that apply' question. For instance, if there are 3 icons per line and a total of 10 icons, the last icon automatically aligns to the left. While fluid content allows for center alignment, it only works when it has 2 options in one row Therefore, for 'Select all that apply' questions, it would be beneficial to have an option for centering, or to extend the fluid content feature to align more than two items per row.