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	$190.59	9.335%	$208.3816	$208.38	$208.40	$208.40
Purchase #2	$131.27	7.339%	$140.9039	$140.90	$140.90	$140.90
Purchase #3	$173.32	12.298%	$194.6349	$194.63	$194.65	$194.60
Purchase #4	$14.98	8.391%	$16.237	$16.24	$16.25	$16.20
Purchase #5	$77.98	9.195%	$85.1503	$85.15	$85.15	$85.20
Purchase #6	$12.87	12.563%	$14.4869	$14.49	$14.50	$14.50
Purchase #7	$90.37	11.204%	$100.4951	$100.50	$100.50	$100.50
7 purchase totals =	$691.38		$760.2897	$760.29	$760.35	$760.30