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	$112.94	8.810%	$122.89	$122.89	$122.90	$122.90
Purchase #2	$151.87	13.729%	$172.7202	$172.72	$172.70	$172.70
Purchase #3	$190.60	7.676%	$205.2305	$205.23	$205.25	$205.20
Purchase #4	$237.99	10.189%	$262.2388	$262.24	$262.25	$262.20
Purchase #5	$145.82	3.255%	$150.5664	$150.57	$150.55	$150.60
Purchase #6	$149.98	11.244%	$166.8438	$166.84	$166.85	$166.80
Purchase #7	$100.62	5.312%	$105.9649	$105.96	$105.95	$106.00
7 purchase totals =	$1,089.82		$1,186.4546	$1,186.45	$1,186.45	$1,186.40