depending on how rest of form is done...
you can wrap them in divs
<div style='float:left;width:100px'>checkbox and text</div>
then after every fifth one you add 'clear:left' to style
(e.g on 6th,11th 16th)
tables are (just) permitted by the css police on this too but would use similar logic
just as easy if outputtting from an array or sql select..