When rounding to the nearest whole number, numbers from X.50 upward round to X+1; numbers below X.50 round down to X.

Greatest value that rounds to 3: must be below 3.50. With 2 decimal places, the greatest is 3.49.

A number rounds to 3 if it is at least 2.50 and less than 3.50.
The greatest possible value with 2 decimal places is just below 3.50.
Greatest X	=	3.49
Check: 3.49 rounded to nearest whole -> look at tenths digit (4) -> round down to 3. 3.50 would round to 4.