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	$172.96	13.479%	$196.2733	$196.27	$196.25	$196.30
Purchase #2	$180.60	13.758%	$205.4469	$205.45	$205.45	$205.40
Purchase #3	$234.55	5.681%	$247.8748	$247.87	$247.85	$247.90
Purchase #4	$179.27	10.239%	$197.6255	$197.63	$197.65	$197.60
Purchase #5	$222.46	12.769%	$250.8659	$250.87	$250.85	$250.90
Purchase #6	$176.77	8.214%	$191.2899	$191.29	$191.30	$191.30
Purchase #7	$118.92	7.395%	$127.7141	$127.71	$127.70	$127.70
7 purchase totals =	$1,285.53		$1,417.0904	$1,417.09	$1,417.05	$1,417.10