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	$9.52	10.615%	$10.5305	$10.53	$10.55	$10.50
Purchase #2	$224.68	12.557%	$252.8931	$252.89	$252.90	$252.90
Purchase #3	$12.59	10.675%	$13.934	$13.93	$13.95	$13.90
Purchase #4	$200.31	9.445%	$219.2293	$219.23	$219.25	$219.20
Purchase #5	$6.67	7.671%	$7.1817	$7.18	$7.20	$7.20
Purchase #6	$214.93	3.531%	$222.5192	$222.52	$222.50	$222.50
Purchase #7	$226.86	10.562%	$250.821	$250.82	$250.80	$250.80
7 purchase totals =	$895.56		$977.1088	$977.10	$977.15	$977.00