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	$131.73	7.400%	$141.478	$141.48	$141.50	$141.50
Purchase #2	$162.72	6.724%	$173.6613	$173.66	$173.65	$173.70
Purchase #3	$160.47	8.325%	$173.8291	$173.83	$173.85	$173.80
Purchase #4	$55.80	7.105%	$59.7646	$59.76	$59.75	$59.80
Purchase #5	$225.63	13.144%	$255.2868	$255.29	$255.30	$255.30
Purchase #6	$159.73	7.788%	$172.1698	$172.17	$172.15	$172.20
Purchase #7	$149.86	10.777%	$166.0104	$166.01	$166.00	$166.00
7 purchase totals =	$1,045.94		$1,142.2000	$1,142.20	$1,142.20	$1,142.30