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	$144.29	3.614%	$149.5046	$149.50	$149.50	$149.50
Purchase #2	$179.27	7.733%	$193.1329	$193.13	$193.15	$193.10
Purchase #3	$205.70	5.700%	$217.4249	$217.42	$217.40	$217.40
Purchase #4	$111.98	13.721%	$127.3448	$127.34	$127.35	$127.30
Purchase #5	$100.79	11.215%	$112.0936	$112.09	$112.10	$112.10
Purchase #6	$165.30	13.134%	$187.0105	$187.01	$187.00	$187.00
Purchase #7	$40.71	4.367%	$42.4878	$42.49	$42.50	$42.50
7 purchase totals =	$948.04		$1,028.9991	$1,028.98	$1,029.00	$1,028.90