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	$160.98	5.509%	$169.8484	$169.85	$169.85	$169.80
Purchase #2	$44.42	8.462%	$48.1788	$48.18	$48.20	$48.20
Purchase #3	$21.95	12.823%	$24.7646	$24.76	$24.75	$24.80
Purchase #4	$220.54	9.706%	$241.9456	$241.95	$241.95	$241.90
Purchase #5	$172.54	4.520%	$180.3388	$180.34	$180.35	$180.30
Purchase #6	$232.90	10.173%	$256.5929	$256.59	$256.60	$256.60
Purchase #7	$51.60	10.139%	$56.8317	$56.83	$56.85	$56.80
7 purchase totals =	$904.93		$978.5008	$978.50	$978.55	$978.40