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	$151.73	9.726%	$166.4873	$166.49	$166.50	$166.50
Purchase #2	$106.97	4.382%	$111.6574	$111.66	$111.65	$111.70
Purchase #3	$249.87	5.521%	$263.6653	$263.67	$263.65	$263.70
Purchase #4	$219.32	4.189%	$228.5073	$228.51	$228.50	$228.50
Purchase #5	$83.65	7.125%	$89.6101	$89.61	$89.60	$89.60
Purchase #6	$132.35	10.522%	$146.2759	$146.28	$146.30	$146.30
Purchase #7	$48.33	13.263%	$54.74	$54.74	$54.75	$54.70
7 purchase totals =	$992.22		$1,060.9433	$1,060.96	$1,060.95	$1,061.00