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	$49.71	9.128%	$54.2475	$54.25	$54.25	$54.20
Purchase #2	$74.56	5.420%	$78.6012	$78.60	$78.60	$78.60
Purchase #3	$63.53	4.293%	$66.2573	$66.26	$66.25	$66.30
Purchase #4	$56.25	6.577%	$59.9496	$59.95	$59.95	$59.90
Purchase #5	$128.90	8.775%	$140.211	$140.21	$140.20	$140.20
Purchase #6	$44.72	8.634%	$48.5811	$48.58	$48.60	$48.60
Purchase #7	$30.75	8.683%	$33.42	$33.42	$33.40	$33.40
7 purchase totals =	$448.42		$481.2677	$481.27	$481.25	$481.20