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	$238.46	7.180%	$255.5814	$255.58	$255.60	$255.60
Purchase #2	$237.61	3.300%	$245.4511	$245.45	$245.45	$245.50
Purchase #3	$110.72	13.709%	$125.8986	$125.90	$125.90	$125.90
Purchase #4	$137.72	7.733%	$148.3699	$148.37	$148.35	$148.40
Purchase #5	$138.64	4.399%	$144.7388	$144.74	$144.75	$144.70
Purchase #6	$192.95	12.763%	$217.5762	$217.58	$217.60	$217.60
Purchase #7	$10.69	5.570%	$11.2854	$11.29	$11.30	$11.30
7 purchase totals =	$1,066.79		$1,148.9014	$1,148.91	$1,148.95	$1,149.00