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	$143.72	5.258%	$151.2768	$151.28	$151.30	$151.30
Purchase #2	$225.33	3.646%	$233.5455	$233.55	$233.55	$233.50
Purchase #3	$58.27	4.777%	$61.0536	$61.05	$61.05	$61.10
Purchase #4	$161.92	5.554%	$170.913	$170.91	$170.90	$170.90
Purchase #5	$212.57	5.130%	$223.4748	$223.47	$223.45	$223.50
Purchase #6	$158.29	9.239%	$172.9144	$172.91	$172.90	$172.90
Purchase #7	$30.51	13.334%	$34.5782	$34.58	$34.60	$34.60
7 purchase totals =	$990.61		$1,047.7563	$1,047.75	$1,047.75	$1,047.80