when is it proper to use grounds for/grounds to?

"Grounds" can have more than one meaning, but I suspect your question has to do when it's meant as "basis."

The general idea is "grounds to INFINITIVE" or "grounds for NOUN".

Examples:

The worker's actions were not considered grounds for dismissal.
It is not clear whether the confession comprises sufficient grounds to pursue an investigation of the matter.

i believe that "grounds for" is always the preferred form in formal written english. so, instead of "grounds to VERB", you'd write "grounds for VERBing".

if there are any examples of official problems contradicting this usage, i haven't seen them.