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	$142.25	6.366%	$151.3056	$151.31	$151.30	$151.30
Purchase #2	$129.33	4.286%	$134.8731	$134.87	$134.85	$134.90
Purchase #3	$185.42	10.821%	$205.4843	$205.48	$205.50	$205.50
Purchase #4	$58.47	13.419%	$66.3161	$66.32	$66.30	$66.30
Purchase #5	$190.26	10.603%	$210.4333	$210.43	$210.45	$210.40
Purchase #6	$154.97	4.643%	$162.1653	$162.17	$162.15	$162.20
Purchase #7	$83.82	4.538%	$87.6238	$87.62	$87.60	$87.60
7 purchase totals =	$944.52		$1,018.2015	$1,018.20	$1,018.15	$1,018.20