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	$151.35	3.698%	$156.9469	$156.95	$156.95	$156.90
Purchase #2	$143.83	9.276%	$157.1717	$157.17	$157.15	$157.20
Purchase #3	$196.57	12.733%	$221.5993	$221.60	$221.60	$221.60
Purchase #4	$161.52	9.142%	$176.2862	$176.29	$176.30	$176.30
Purchase #5	$67.61	5.629%	$71.4158	$71.42	$71.40	$71.40
Purchase #6	$77.76	12.649%	$87.5959	$87.60	$87.60	$87.60
Purchase #7	$229.68	3.863%	$238.5525	$238.55	$238.55	$238.60
7 purchase totals =	$1,028.32		$1,109.5683	$1,109.58	$1,109.55	$1,109.60