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	$43.47	7.154%	$46.5798	$46.58	$46.60	$46.60
Purchase #2	$104.50	11.678%	$116.7035	$116.70	$116.70	$116.70
Purchase #3	$215.42	6.205%	$228.7868	$228.79	$228.80	$228.80
Purchase #4	$89.89	9.327%	$98.274	$98.27	$98.25	$98.30
Purchase #5	$153.74	12.184%	$172.4717	$172.47	$172.45	$172.50
Purchase #6	$86.67	13.637%	$98.4892	$98.49	$98.50	$98.50
Purchase #7	$24.71	4.509%	$25.8242	$25.82	$25.80	$25.80
7 purchase totals =	$718.40		$787.1292	$787.12	$787.10	$787.20