Why does start transaction and rollback fail to rollback when running scripts in MySQL 5?

I have the following script...

START TRANSACTION;

INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-114, NULL, NULL, 'c21_1.jpg', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-115, NULL, NULL, 'c21_2.jpg', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-116, NULL, NULL, 'c21_3.jpg', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-117, NULL, NULL, 'c21_4.gif', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-118, NULL, NULL, 'c21_5.gif', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-119, NULL, NULL, 'c21_6.gif', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-120, NULL, NULL, 'c21_7.gif', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-121, NULL, NULL, 'AIRMILES_MIN_RBLUE.png', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-122, NULL, NULL, 'c21_logo_commercial-WHT.png', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-123, NULL, NULL, 'c21_logo_fhe_pms124-WHT.png', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-124, NULL, NULL, 'CENTURY-21-Logo-Century21.png', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-125, NULL, NULL, 'Easter-Seals-Logos-2005-008-1.png', NULL);
INSERT INTO `Image` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-126, NULL, NULL, 'Easter-Seals-Logos-2005-008-2.png', NULL);
INSERT INTO `Imag开发者_运维百科e` (`id`,`created`,`deleted`,`fileName`,`used`) VALUES (-127, NULL, NULL, 'kids-to-camp-EN.png', NULL);



INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -115);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -116);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -117);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -118);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -119);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -120);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -121);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -122);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -123);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -124);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -125);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -126);
INSERT INTO `AgencyImage` (`agency_id`,`image_id`) VALUES   (1, -127);


ROLLBACK;

I wanted to validate the script ran before commiting the code. However the first time this ran it did not roll anything back.

What am I doing wrong?

Is it a MyISAM table? If so, you need to switch to InnoDB if you want to use transactions. If you're running the queries from something like PHP, make sure you have autocommit turned off.