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	$219.77	4.679%	$230.053	$230.05	$230.05	$230.10
Purchase #2	$221.51	7.562%	$238.2606	$238.26	$238.25	$238.30
Purchase #3	$133.53	13.292%	$151.2788	$151.28	$151.30	$151.30
Purchase #4	$67.33	6.237%	$71.5294	$71.53	$71.55	$71.50
Purchase #5	$185.72	4.171%	$193.4664	$193.47	$193.45	$193.50
Purchase #6	$85.97	6.861%	$91.8684	$91.87	$91.85	$91.90
Purchase #7	$38.69	5.255%	$40.7232	$40.72	$40.70	$40.70
7 purchase totals =	$952.52		$1,017.1798	$1,017.18	$1,017.15	$1,017.30