Can I get into NIT Trichy CSE with 99.9058580 in the JEE Main 2021?

Yes, you have a good chance of becoming eligible at NIT Trichy. Since your score is what you have mentioned above, it translates to your rank being somewhere 1,000 or 1,200. As per your rank, you have a sharper edge at securing admission in the CSE department of NIT Trichy. 

However, here is a detailed cut-off list of NIT Trichy for equivalent disciplines, alongside CSE as well:

Apart from this, you can also vividly research more about other rounds, and categories, at your convenience. Hope this helps answer your question, wish you all the best!