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	$133.25	9.271%	$145.6036	$145.60	$145.60	$145.60
Purchase #2	$63.72	12.492%	$71.6799	$71.68	$71.70	$71.70
Purchase #3	$118.41	3.448%	$122.4928	$122.49	$122.50	$122.50
Purchase #4	$249.89	10.139%	$275.2263	$275.23	$275.25	$275.20
Purchase #5	$134.60	12.140%	$150.9404	$150.94	$150.95	$150.90
Purchase #6	$111.76	13.382%	$126.7157	$126.72	$126.70	$126.70
Purchase #7	$164.63	6.827%	$175.8693	$175.87	$175.85	$175.90
7 purchase totals =	$976.26		$1,068.5280	$1,068.53	$1,068.55	$1,068.50