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	$223.64	7.510%	$240.4354	$240.44	$240.45	$240.40
Purchase #2	$190.29	3.345%	$196.6552	$196.66	$196.65	$196.70
Purchase #3	$66.52	5.763%	$70.3535	$70.35	$70.35	$70.40
Purchase #4	$103.98	8.316%	$112.627	$112.63	$112.65	$112.60
Purchase #5	$135.84	5.823%	$143.75	$143.75	$143.75	$143.80
Purchase #6	$103.40	11.804%	$115.6053	$115.61	$115.60	$115.60
Purchase #7	$48.70	10.594%	$53.8593	$53.86	$53.85	$53.90
7 purchase totals =	$872.37		$933.2857	$933.30	$933.30	$933.40