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	$142.58	4.185%	$148.547	$148.55	$148.55	$148.50
Purchase #2	$127.70	9.238%	$139.4969	$139.50	$139.50	$139.50
Purchase #3	$208.97	13.271%	$236.7024	$236.70	$236.70	$236.70
Purchase #4	$91.25	8.733%	$99.2189	$99.22	$99.20	$99.20
Purchase #5	$47.26	10.138%	$52.0512	$52.05	$52.05	$52.10
Purchase #6	$238.27	7.694%	$256.6025	$256.60	$256.60	$256.60
Purchase #7	$88.65	13.738%	$100.8287	$100.83	$100.85	$100.80
7 purchase totals =	$944.68		$1,033.4476	$1,033.45	$1,033.45	$1,033.40