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	$132.92	9.389%	$145.3999	$145.40	$145.40	$145.40
Purchase #2	$127.84	8.162%	$138.2743	$138.27	$138.25	$138.30
Purchase #3	$184.48	7.404%	$198.1389	$198.14	$198.15	$198.10
Purchase #4	$243.64	7.395%	$261.6572	$261.66	$261.65	$261.70
Purchase #5	$43.54	4.312%	$45.4174	$45.42	$45.40	$45.40
Purchase #6	$191.78	13.211%	$217.1161	$217.12	$217.10	$217.10
Purchase #7	$66.78	8.544%	$72.4857	$72.49	$72.50	$72.50
7 purchase totals =	$990.98		$1,078.4895	$1,078.50	$1,078.45	$1,078.50