What is the grammatical rationale for using the imperfective "рассыпа́ться" or the perfective "рассы́паться"?

Question

> Это все хорошо. Но ни к чему **рассыпаться** из-за таких пустяков в благодарностях.Тhis comes from one of the grammar-related questions in the most advanced level of the national Russian proficiency test that I've recently took in my country. The question was about whether to use the imperfective "**рассыпа́ться**" or the perfective "**рассы́паться**", even if the difference in accent is only one syllable apart from one another.I chose the imperfective "рассыпа́ться", drawing on the fact that in conversation I tend to use imperfective verbs in the case of "незачем", but I'm not sure of the grammatical rationale for it.

Answer 1

I chose the imperfective "рассыпа́ться",

You chose correctly.

Thе imperfective infinitive is used to express prohibition or inadvisability. It is used after words:

нe нaдо, нe нyжно, не следует, не принято, не полагается, не советую, не стоит, не полагается, не хочется, незачем