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	$108.31	3.232%	$111.8106	$111.81	$111.80	$111.80
Purchase #2	$19.31	10.199%	$21.2794	$21.28	$21.30	$21.30
Purchase #3	$163.51	11.855%	$182.8941	$182.89	$182.90	$182.90
Purchase #4	$225.42	11.851%	$252.1345	$252.13	$252.15	$252.10
Purchase #5	$151.43	11.225%	$168.428	$168.43	$168.45	$168.40
Purchase #6	$67.28	4.490%	$70.3009	$70.30	$70.30	$70.30
Purchase #7	$119.79	12.495%	$134.7578	$134.76	$134.75	$134.80
7 purchase totals =	$855.05		$941.6053	$941.60	$941.65	$941.60