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	$227.55	6.631%	$242.6388	$242.64	$242.65	$242.60
Purchase #2	$41.98	7.184%	$44.9958	$45.00	$45.00	$45.00
Purchase #3	$83.86	8.348%	$90.8606	$90.86	$90.85	$90.90
Purchase #4	$205.87	10.520%	$227.5275	$227.53	$227.55	$227.50
Purchase #5	$199.55	3.163%	$205.8618	$205.86	$205.85	$205.90
Purchase #6	$92.31	13.169%	$104.4663	$104.47	$104.45	$104.50
Purchase #7	$39.78	8.798%	$43.2798	$43.28	$43.30	$43.30
7 purchase totals =	$890.90		$959.6306	$959.64	$959.65	$959.70