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	$140.71	7.827%	$151.7234	$151.72	$151.70	$151.70
Purchase #2	$65.50	9.786%	$71.9098	$71.91	$71.90	$71.90
Purchase #3	$138.91	9.132%	$151.5953	$151.60	$151.60	$151.60
Purchase #4	$178.81	8.403%	$193.8354	$193.84	$193.85	$193.80
Purchase #5	$16.94	7.527%	$18.2151	$18.22	$18.20	$18.20
Purchase #6	$190.73	7.729%	$205.4715	$205.47	$205.45	$205.50
Purchase #7	$190.65	10.551%	$210.7655	$210.77	$210.75	$210.80
7 purchase totals =	$922.25		$1,003.5160	$1,003.53	$1,003.45	$1,003.50