Something like rounding is not done very often for most people. Maybe the nearest they come is just rounding up a restaurant bill, and that's to no specific rules.
So, when a question like this arises, I can sympathise with someone giving it a bash and believing it to be correct. It's just lack of practice.
Even the idea of rounding up from the least significant digit is 'almost convicing' when it's just 3 digits or so.... until you think it through and figure it can't be right if there's 400 digits!
You get the same with physics where some explanations are so plausible, you almost start believing them yourself (if you jump up during a flight, you'll end up at the back of the plane!). Complete bollocks of course.