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	$145.39	8.434%	$157.6522	$157.65	$157.65	$157.70
Purchase #2	$43.37	11.630%	$48.4139	$48.41	$48.40	$48.40
Purchase #3	$234.87	5.336%	$247.4027	$247.40	$247.40	$247.40
Purchase #4	$239.50	11.208%	$266.3432	$266.34	$266.35	$266.30
Purchase #5	$131.60	11.287%	$146.4537	$146.45	$146.45	$146.50
Purchase #6	$144.96	4.770%	$151.8746	$151.87	$151.85	$151.90
Purchase #7	$41.84	4.324%	$43.6492	$43.65	$43.65	$43.60
7 purchase totals =	$981.53		$1,061.7895	$1,061.77	$1,061.75	$1,061.80