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	$111.69	6.302%	$118.7287	$118.73	$118.75	$118.70
Purchase #2	$45.31	11.395%	$50.4731	$50.47	$50.45	$50.50
Purchase #3	$50.56	6.827%	$54.0117	$54.01	$54.00	$54.00
Purchase #4	$200.51	13.790%	$228.1603	$228.16	$228.15	$228.20
Purchase #5	$13.64	3.169%	$14.0723	$14.07	$14.05	$14.10
Purchase #6	$29.91	9.149%	$32.6465	$32.65	$32.65	$32.60
Purchase #7	$194.90	5.615%	$205.8436	$205.84	$205.85	$205.80
7 purchase totals =	$646.52		$703.9362	$703.93	$703.90	$703.90