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	$133.35	9.111%	$145.4995	$145.50	$145.50	$145.50
Purchase #2	$94.32	5.664%	$99.6623	$99.66	$99.65	$99.70
Purchase #3	$230.79	3.323%	$238.4592	$238.46	$238.45	$238.50
Purchase #4	$60.35	9.644%	$66.1702	$66.17	$66.15	$66.20
Purchase #5	$139.86	8.289%	$151.453	$151.45	$151.45	$151.50
Purchase #6	$148.67	12.449%	$167.1779	$167.18	$167.20	$167.20
Purchase #7	$191.91	11.597%	$214.1658	$214.17	$214.15	$214.20
7 purchase totals =	$999.25		$1,082.5879	$1,082.59	$1,082.55	$1,082.80