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	$140.35	3.496%	$145.2566	$145.26	$145.25	$145.30
Purchase #2	$90.77	9.810%	$99.6745	$99.67	$99.65	$99.70
Purchase #3	$138.45	4.635%	$144.8672	$144.87	$144.85	$144.90
Purchase #4	$131.29	7.323%	$140.9044	$140.90	$140.90	$140.90
Purchase #5	$170.71	8.773%	$185.6864	$185.69	$185.70	$185.70
Purchase #6	$92.73	10.733%	$102.6827	$102.68	$102.70	$102.70
Purchase #7	$196.90	11.512%	$219.5671	$219.57	$219.55	$219.60
7 purchase totals =	$961.20		$1,038.6389	$1,038.64	$1,038.60	$1,038.80