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	$153.36	5.670%	$162.0555	$162.06	$162.05	$162.10
Purchase #2	$54.76	6.750%	$58.4563	$58.46	$58.45	$58.50
Purchase #3	$125.77	3.845%	$130.6059	$130.61	$130.60	$130.60
Purchase #4	$242.53	5.500%	$255.8692	$255.87	$255.85	$255.90
Purchase #5	$113.86	10.823%	$126.1831	$126.18	$126.20	$126.20
Purchase #6	$60.45	7.342%	$64.8882	$64.89	$64.90	$64.90
Purchase #7	$159.30	7.440%	$171.1519	$171.15	$171.15	$171.20
7 purchase totals =	$910.03		$969.2101	$969.22	$969.20	$969.40