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	$126.94	3.329%	$131.1658	$131.17	$131.15	$131.20
Purchase #2	$41.77	9.170%	$45.6003	$45.60	$45.60	$45.60
Purchase #3	$152.65	4.664%	$159.7696	$159.77	$159.75	$159.80
Purchase #4	$151.77	4.522%	$158.633	$158.63	$158.65	$158.60
Purchase #5	$10.91	3.559%	$11.2983	$11.30	$11.30	$11.30
Purchase #6	$87.44	5.804%	$92.515	$92.52	$92.50	$92.50
Purchase #7	$151.64	10.464%	$167.5076	$167.51	$167.50	$167.50
7 purchase totals =	$723.12		$766.4896	$766.50	$766.45	$766.50