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	$154.93	4.102%	$161.2852	$161.29	$161.30	$161.30
Purchase #2	$55.32	11.128%	$61.476	$61.48	$61.50	$61.50
Purchase #3	$166.58	11.133%	$185.1254	$185.13	$185.15	$185.10
Purchase #4	$88.96	11.491%	$99.1824	$99.18	$99.20	$99.20
Purchase #5	$153.97	3.336%	$159.1064	$159.11	$159.10	$159.10
Purchase #6	$111.71	3.207%	$115.2925	$115.29	$115.30	$115.30
Purchase #7	$21.51	11.768%	$24.0413	$24.04	$24.05	$24.00
7 purchase totals =	$752.98		$805.5092	$805.52	$805.60	$805.50