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	$233.38	4.831%	$244.6546	$244.65	$244.65	$244.70
Purchase #2	$101.77	11.609%	$113.5845	$113.58	$113.60	$113.60
Purchase #3	$221.82	10.250%	$244.5566	$244.56	$244.55	$244.60
Purchase #4	$58.64	11.568%	$65.4235	$65.42	$65.40	$65.40
Purchase #5	$154.51	9.628%	$169.3862	$169.39	$169.40	$169.40
Purchase #6	$9.50	12.737%	$10.71	$10.71	$10.70	$10.70
Purchase #7	$11.45	6.181%	$12.1577	$12.16	$12.15	$12.20
7 purchase totals =	$791.07		$860.4731	$860.47	$860.45	$860.60