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	$80.72	6.105%	$85.648	$85.65	$85.65	$85.60
Purchase #2	$49.66	4.361%	$51.8257	$51.83	$51.85	$51.80
Purchase #3	$100.98	10.571%	$111.6546	$111.65	$111.65	$111.70
Purchase #4	$41.83	6.634%	$44.605	$44.61	$44.60	$44.60
Purchase #5	$101.93	11.457%	$113.6081	$113.61	$113.60	$113.60
Purchase #6	$62.76	11.220%	$69.8017	$69.80	$69.80	$69.80
Purchase #7	$14.89	6.859%	$15.9113	$15.91	$15.90	$15.90
7 purchase totals =	$452.77		$493.0544	$493.06	$493.05	$493.00