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	$74.46	11.268%	$82.8502	$82.85	$82.85	$82.90
Purchase #2	$104.59	6.679%	$111.5756	$111.58	$111.60	$111.60
Purchase #3	$201.45	6.623%	$214.792	$214.79	$214.80	$214.80
Purchase #4	$35.56	11.495%	$39.6476	$39.65	$39.65	$39.60
Purchase #5	$204.99	12.630%	$230.8802	$230.88	$230.90	$230.90
Purchase #6	$124.59	6.314%	$132.4566	$132.46	$132.45	$132.50
Purchase #7	$56.71	12.513%	$63.8061	$63.81	$63.80	$63.80
7 purchase totals =	$802.35		$876.0083	$876.02	$876.05	$876.10