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	$235.29	8.857%	$256.1296	$256.13	$256.15	$256.10
Purchase #2	$196.83	3.868%	$204.4434	$204.44	$204.45	$204.40
Purchase #3	$86.83	3.255%	$89.6563	$89.66	$89.65	$89.70
Purchase #4	$68.52	4.310%	$71.4732	$71.47	$71.45	$71.50
Purchase #5	$143.71	10.451%	$158.7291	$158.73	$158.75	$158.70
Purchase #6	$183.72	5.612%	$194.0304	$194.03	$194.05	$194.00
Purchase #7	$153.52	9.869%	$168.6709	$168.67	$168.65	$168.70
7 purchase totals =	$1,068.42		$1,143.1329	$1,143.13	$1,143.15	$1,143.10