ROUND(X), ROUND(X,D) rounds the argument X to D decimal places. : ROUND « Math Numeric Functions « MySQL Tutorial

1. MySQL Tutorial
2. Math Numeric Functions
3. ROUND

1. D defaults to 0 if not specified.
2. D can be negative to cause D digits left of the decimal point of the value X to become zero.

mysql>
mysql> SELECT ROUND(-1.23);
+--------------+
| ROUND(-1.23) |
+--------------+
|           -1 |
+--------------+
1 row in set (0.00 sec)

mysql> SELECT ROUND(-1.58);
+--------------+
| ROUND(-1.58) |
+--------------+
|           -2 |
+--------------+
1 row in set (0.00 sec)

mysql> SELECT ROUND(1.58);
+-------------+
| ROUND(1.58) |
+-------------+
|           2 |
+-------------+
1 row in set (0.00 sec)