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	$214.71	7.516%	$230.8476	$230.85	$230.85	$230.80
Purchase #2	$158.61	3.275%	$163.8045	$163.80	$163.80	$163.80
Purchase #3	$52.45	9.415%	$57.3882	$57.39	$57.40	$57.40
Purchase #4	$19.92	5.524%	$21.0204	$21.02	$21.00	$21.00
Purchase #5	$229.32	11.231%	$255.0749	$255.07	$255.05	$255.10
Purchase #6	$48.29	11.469%	$53.8284	$53.83	$53.85	$53.80
Purchase #7	$134.85	12.445%	$151.6321	$151.63	$151.65	$151.60
7 purchase totals =	$858.15		$933.5961	$933.59	$933.60	$933.50