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	$89.38	3.277%	$92.309	$92.31	$92.30	$92.30
Purchase #2	$42.60	13.868%	$48.5078	$48.51	$48.50	$48.50
Purchase #3	$101.42	10.164%	$111.7283	$111.73	$111.75	$111.70
Purchase #4	$67.25	12.758%	$75.8298	$75.83	$75.85	$75.80
Purchase #5	$208.75	11.481%	$232.7166	$232.72	$232.70	$232.70
Purchase #6	$46.86	11.630%	$52.3098	$52.31	$52.30	$52.30
Purchase #7	$144.73	6.564%	$154.2301	$154.23	$154.25	$154.20
7 purchase totals =	$700.99		$767.6314	$767.64	$767.65	$767.50