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	$204.60	8.776%	$222.5557	$222.56	$222.55	$222.60
Purchase #2	$115.69	3.263%	$119.465	$119.47	$119.45	$119.50
Purchase #3	$198.85	11.548%	$221.8132	$221.81	$221.80	$221.80
Purchase #4	$126.72	12.176%	$142.1494	$142.15	$142.15	$142.10
Purchase #5	$139.48	10.789%	$154.5285	$154.53	$154.55	$154.50
Purchase #6	$78.54	9.390%	$85.9149	$85.91	$85.90	$85.90
Purchase #7	$250.50	11.415%	$279.0946	$279.09	$279.10	$279.10
7 purchase totals =	$1,114.38		$1,225.5213	$1,225.52	$1,225.50	$1,225.50