First of all,I would like to say you that you can't predict about the marks very accurately so rank should be the parameter.

Coming to NITs, there are 3 tiers of them.Not all NITs are the same. If you want to get CSE in any of the tier 1 NIT, then your rank should be <2000 in JEE MAIN.

If you want CSE in any of the tier 2 NITs, then your rank should not exceed 5000 in JEE MAIN.

And if you just want an NIT tag (which you shouldn't as NIT tag is not any big tag),then for CSE your rank should be less than 10,000.

And if I convert the above stated ranks into minimum marks required in JEE MAIN (remember it can change drastically depending upon the paper),as originally asked. Then this will be the data.

CSE in:-

Tier 1 NITs - 245

Tier 2 NITs - 220

Tier 3 NITs - 200