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	$92.95	11.283%	$103.4375	$103.44	$103.45	$103.40
Purchase #2	$46.55	4.495%	$48.6424	$48.64	$48.65	$48.60
Purchase #3	$43.51	11.315%	$48.4332	$48.43	$48.45	$48.40
Purchase #4	$38.26	4.592%	$40.0169	$40.02	$40.00	$40.00
Purchase #5	$24.67	7.680%	$26.5647	$26.56	$26.55	$26.60
Purchase #6	$103.70	12.509%	$116.6718	$116.67	$116.65	$116.70
Purchase #7	$47.65	10.868%	$52.8286	$52.83	$52.85	$52.80
7 purchase totals =	$397.29		$436.5951	$436.59	$436.60	$436.50