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	$219.46	10.519%	$242.545	$242.55	$242.55	$242.50
Purchase #2	$226.58	8.346%	$245.4904	$245.49	$245.50	$245.50
Purchase #3	$85.52	4.688%	$89.5292	$89.53	$89.55	$89.50
Purchase #4	$37.73	5.366%	$39.7546	$39.75	$39.75	$39.80
Purchase #5	$17.68	4.248%	$18.431	$18.43	$18.45	$18.40
Purchase #6	$173.56	3.152%	$179.0306	$179.03	$179.05	$179.00
Purchase #7	$134.57	7.385%	$144.508	$144.51	$144.50	$144.50
7 purchase totals =	$895.10		$959.2888	$959.29	$959.35	$959.20