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	$238.52	9.370%	$260.8693	$260.87	$260.85	$260.90
Purchase #2	$176.64	3.107%	$182.1282	$182.13	$182.15	$182.10
Purchase #3	$195.83	13.750%	$222.7566	$222.76	$222.75	$222.80
Purchase #4	$89.29	12.541%	$100.4879	$100.49	$100.50	$100.50
Purchase #5	$191.94	7.598%	$206.5236	$206.52	$206.50	$206.50
Purchase #6	$46.87	3.316%	$48.4242	$48.42	$48.40	$48.40
Purchase #7	$125.84	3.532%	$130.2847	$130.28	$130.30	$130.30
7 purchase totals =	$1,064.93		$1,151.4745	$1,151.47	$1,151.45	$1,151.50