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	$94.59	11.128%	$105.116	$105.12	$105.10	$105.10
Purchase #2	$63.49	11.382%	$70.7164	$70.72	$70.70	$70.70
Purchase #3	$54.77	5.306%	$57.6761	$57.68	$57.70	$57.70
Purchase #4	$92.35	3.245%	$95.3468	$95.35	$95.35	$95.30
Purchase #5	$84.95	5.208%	$89.3742	$89.37	$89.35	$89.40
Purchase #6	$179.58	11.154%	$199.6104	$199.61	$199.60	$199.60
Purchase #7	$44.47	10.798%	$49.2719	$49.27	$49.25	$49.30
7 purchase totals =	$614.20		$667.1118	$667.12	$667.05	$667.10