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	$43.37	7.137%	$46.4653	$46.47	$46.45	$46.50
Purchase #2	$48.75	6.338%	$51.8398	$51.84	$51.85	$51.80
Purchase #3	$154.78	6.717%	$165.1766	$165.18	$165.20	$165.20
Purchase #4	$31.94	11.267%	$35.5387	$35.54	$35.55	$35.50
Purchase #5	$242.62	5.243%	$255.3406	$255.34	$255.35	$255.30
Purchase #6	$132.82	11.514%	$148.1129	$148.11	$148.10	$148.10
Purchase #7	$228.40	7.396%	$245.2925	$245.29	$245.30	$245.30
7 purchase totals =	$882.68		$947.7664	$947.77	$947.80	$947.70