Let's round decimal by decimal until we get two significant figures. When the successor number is smaller than 5 then the predecessor number remains the same. When the successor number is greater than 5 then the predecessor number rounds to the first greater number. If the successor number is 5 then the even predecessor number remains the same and the odd predecessor number rounds to the first greater number. 0.002353 ≈ 0.00235 0.00235 ≈ 0.0024
