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	$157.95	4.191%	$164.5697	$164.57	$164.55	$164.60
Purchase #2	$100.58	3.872%	$104.4745	$104.47	$104.45	$104.50
Purchase #3	$212.54	8.534%	$230.6782	$230.68	$230.70	$230.70
Purchase #4	$207.52	11.351%	$231.0756	$231.08	$231.10	$231.10
Purchase #5	$118.60	7.669%	$127.6954	$127.70	$127.70	$127.70
Purchase #6	$105.71	3.275%	$109.172	$109.17	$109.15	$109.20
Purchase #7	$172.89	11.550%	$192.8588	$192.86	$192.85	$192.90
7 purchase totals =	$1,075.79		$1,160.5242	$1,160.53	$1,160.50	$1,160.70