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	$152.93	3.492%	$158.2703	$158.27	$158.25	$158.30
Purchase #2	$47.26	5.180%	$49.7081	$49.71	$49.70	$49.70
Purchase #3	$76.71	11.369%	$85.4312	$85.43	$85.45	$85.40
Purchase #4	$59.31	5.434%	$62.5329	$62.53	$62.55	$62.50
Purchase #5	$96.88	12.391%	$108.8844	$108.88	$108.90	$108.90
Purchase #6	$239.69	13.858%	$272.9062	$272.91	$272.90	$272.90
Purchase #7	$170.79	6.478%	$181.8538	$181.85	$181.85	$181.90
7 purchase totals =	$843.57		$919.5869	$919.58	$919.60	$919.60