HELLO PRAKASH

It is very difficult to enter into top 5 NITS and getting a cs branch in in it is avery challenging Job but do not worry you can do it with a proper strategy.
i will  tell you about minimum first the min rank you should bring ist at least 1k max can be upto 2k  just to be on safer side if we talk in terms of percentile your percentile should be greater that 99.6+

this is the link of previous year cutoffs for top  NITs https://engineering.careers360.com/articles/jee-main-cutoff-for-top-nits

HOPE IT HELPS!!