I’d say that depends on how much effort he’s willing to let you put into the estimates. It’s often possible to de-risk estimates to that degree, but that basically requires putting in a significant chunk of the work up front to break the problem down and research all the unknowns.

If your boss wants that level of certainty, you should ask him to teach you how to achieve it and see how he thinks such a thing is possible. I’m not suggesting he’s not delusional. Just that if you pick his brain and then ask how to deal with the types of uncertainty you’re concerned about, you’re more likely to get to a place where you and the boss are aligned. (This assumes your boss is an even vaguely reasonable human being, tho. YMMV.)