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	$98.95	3.486%	$102.3994	$102.40	$102.40	$102.40
Purchase #2	$239.65	10.733%	$265.3716	$265.37	$265.35	$265.40
Purchase #3	$90.81	10.756%	$100.5775	$100.58	$100.60	$100.60
Purchase #4	$23.94	6.103%	$25.4011	$25.40	$25.40	$25.40
Purchase #5	$167.77	10.622%	$185.5905	$185.59	$185.60	$185.60
Purchase #6	$136.28	12.613%	$153.469	$153.47	$153.45	$153.50
Purchase #7	$205.83	4.136%	$214.3431	$214.34	$214.35	$214.30
7 purchase totals =	$963.23		$1,047.1522	$1,047.15	$1,047.15	$1,047.20