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	$99.60	8.297%	$107.8638	$107.86	$107.85	$107.90
Purchase #2	$111.82	5.313%	$117.761	$117.76	$117.75	$117.80
Purchase #3	$46.59	9.327%	$50.9354	$50.94	$50.95	$50.90
Purchase #4	$176.74	13.628%	$200.8261	$200.83	$200.85	$200.80
Purchase #5	$139.79	13.184%	$158.2199	$158.22	$158.20	$158.20
Purchase #6	$132.30	3.635%	$137.1091	$137.11	$137.10	$137.10
Purchase #7	$84.90	5.361%	$89.4515	$89.45	$89.45	$89.50
7 purchase totals =	$791.74		$862.1668	$862.17	$862.15	$862.20