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	$183.66	3.420%	$189.9412	$189.94	$189.95	$189.90
Purchase #2	$190.90	5.500%	$201.3995	$201.40	$201.40	$201.40
Purchase #3	$104.27	6.738%	$111.2957	$111.30	$111.30	$111.30
Purchase #4	$116.82	5.801%	$123.5967	$123.60	$123.60	$123.60
Purchase #5	$121.62	13.325%	$137.8259	$137.83	$137.85	$137.80
Purchase #6	$212.61	11.552%	$237.1707	$237.17	$237.15	$237.20
Purchase #7	$159.39	12.235%	$178.8914	$178.89	$178.90	$178.90
7 purchase totals =	$1,089.27		$1,180.1211	$1,180.13	$1,180.15	$1,180.10