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	$62.49	6.439%	$66.5137	$66.51	$66.50	$66.50
Purchase #2	$107.55	10.734%	$119.0944	$119.09	$119.10	$119.10
Purchase #3	$248.77	5.745%	$263.0618	$263.06	$263.05	$263.10
Purchase #4	$183.89	3.539%	$190.3979	$190.40	$190.40	$190.40
Purchase #5	$23.27	8.383%	$25.2207	$25.22	$25.20	$25.20
Purchase #6	$210.35	11.519%	$234.5802	$234.58	$234.60	$234.60
Purchase #7	$173.89	6.689%	$185.5215	$185.52	$185.50	$185.50
7 purchase totals =	$1,010.21		$1,084.3902	$1,084.38	$1,084.35	$1,084.40