This would be rounded up to 4.06. When the number after the last number you want is 0, 1, 2, 3, or 4, you keep the last number the same. If the number after the last number you want is 5, 6, 7, 8, or 9, you round the last number you want up one more.
If this was instead 4.054, it would instead round to 4.054.
