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	$57.58	7.390%	$61.8352	$61.84	$61.85	$61.80
Purchase #2	$204.91	12.164%	$229.8353	$229.84	$229.85	$229.80
Purchase #3	$239.71	8.110%	$259.1505	$259.15	$259.15	$259.20
Purchase #4	$125.57	4.516%	$131.2407	$131.24	$131.25	$131.20
Purchase #5	$169.72	11.786%	$189.7232	$189.72	$189.70	$189.70
Purchase #6	$92.64	6.290%	$98.4671	$98.47	$98.45	$98.50
Purchase #7	$122.65	3.859%	$127.3831	$127.38	$127.40	$127.40
7 purchase totals =	$1,012.78		$1,097.6351	$1,097.64	$1,097.65	$1,097.60