Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$10.65	7.432%	$11.4415	$11.44	$11.45	$11.40
Purchase #2	$92.83	7.381%	$99.6818	$99.68	$99.70	$99.70
Purchase #3	$230.55	10.451%	$254.6448	$254.64	$254.65	$254.60
Purchase #4	$10.92	11.305%	$12.1545	$12.15	$12.15	$12.20
Purchase #5	$202.69	9.637%	$222.2232	$222.22	$222.20	$222.20
Purchase #6	$55.58	7.757%	$59.8913	$59.89	$59.90	$59.90
Purchase #7	$220.71	13.681%	$250.9053	$250.91	$250.90	$250.90
7 purchase totals =	$823.93		$910.9424	$910.93	$910.95	$910.90