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	$234.52	10.210%	$258.4645	$258.46	$258.45	$258.50
Purchase #2	$59.56	6.791%	$63.6047	$63.60	$63.60	$63.60
Purchase #3	$167.36	3.117%	$172.5766	$172.58	$172.60	$172.60
Purchase #4	$82.73	5.756%	$87.4919	$87.49	$87.50	$87.50
Purchase #5	$165.37	4.735%	$173.2003	$173.20	$173.20	$173.20
Purchase #6	$70.56	11.212%	$78.4712	$78.47	$78.45	$78.50
Purchase #7	$103.28	8.159%	$111.7066	$111.71	$111.70	$111.70
7 purchase totals =	$883.38		$945.5158	$945.51	$945.50	$945.60