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	$81.39	11.446%	$90.7059	$90.71	$90.70	$90.70
Purchase #2	$127.66	12.307%	$143.3711	$143.37	$143.35	$143.40
Purchase #3	$15.59	4.560%	$16.3009	$16.30	$16.30	$16.30
Purchase #4	$89.65	13.218%	$101.4999	$101.50	$101.50	$101.50
Purchase #5	$103.36	7.494%	$111.1058	$111.11	$111.10	$111.10
Purchase #6	$111.76	8.136%	$120.8528	$120.85	$120.85	$120.90
Purchase #7	$24.32	5.487%	$25.6544	$25.65	$25.65	$25.70
7 purchase totals =	$553.73		$609.4908	$609.49	$609.45	$609.60