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	$95.27	11.769%	$106.4823	$106.48	$106.50	$106.50
Purchase #2	$17.91	5.208%	$18.8428	$18.84	$18.85	$18.80
Purchase #3	$61.33	8.351%	$66.4517	$66.45	$66.45	$66.50
Purchase #4	$37.25	9.155%	$40.6602	$40.66	$40.65	$40.70
Purchase #5	$53.39	5.665%	$56.4145	$56.41	$56.40	$56.40
Purchase #6	$141.46	4.718%	$148.1341	$148.13	$148.15	$148.10
Purchase #7	$96.72	12.176%	$108.4966	$108.50	$108.50	$108.50
7 purchase totals =	$503.33		$545.4822	$545.47	$545.50	$545.50