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	$199.40	3.471%	$206.3212	$206.32	$206.30	$206.30
Purchase #2	$10.31	11.840%	$11.5307	$11.53	$11.55	$11.50
Purchase #3	$136.87	6.590%	$145.8897	$145.89	$145.90	$145.90
Purchase #4	$135.85	7.117%	$145.5184	$145.52	$145.50	$145.50
Purchase #5	$183.71	3.673%	$190.4577	$190.46	$190.45	$190.50
Purchase #6	$73.61	3.156%	$75.9331	$75.93	$75.95	$75.90
Purchase #7	$176.82	8.504%	$191.8568	$191.86	$191.85	$191.90
7 purchase totals =	$916.57		$967.5076	$967.51	$967.50	$967.50