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	$54.80	3.301%	$56.6089	$56.61	$56.60	$56.60
Purchase #2	$108.54	8.295%	$117.5434	$117.54	$117.55	$117.50
Purchase #3	$22.84	11.536%	$25.4748	$25.47	$25.45	$25.50
Purchase #4	$139.96	13.341%	$158.6321	$158.63	$158.65	$158.60
Purchase #5	$210.30	7.548%	$226.1734	$226.17	$226.15	$226.20
Purchase #6	$11.47	12.114%	$12.8595	$12.86	$12.85	$12.90
Purchase #7	$117.75	11.537%	$131.3348	$131.33	$131.35	$131.30
7 purchase totals =	$665.66		$728.6269	$728.61	$728.60	$728.60