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	$208.84	7.538%	$224.5824	$224.58	$224.60	$224.60
Purchase #2	$113.42	4.605%	$118.643	$118.64	$118.65	$118.60
Purchase #3	$128.27	13.289%	$145.3158	$145.32	$145.30	$145.30
Purchase #4	$46.79	10.654%	$51.775	$51.78	$51.80	$51.80
Purchase #5	$138.47	7.269%	$148.5354	$148.54	$148.55	$148.50
Purchase #6	$234.28	10.188%	$258.1484	$258.15	$258.15	$258.10
Purchase #7	$81.29	13.288%	$92.0918	$92.09	$92.10	$92.10
7 purchase totals =	$951.36		$1,039.0918	$1,039.10	$1,039.15	$1,039.00