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	$54.83	10.821%	$60.7632	$60.76	$60.75	$60.80
Purchase #2	$144.91	4.790%	$151.8512	$151.85	$151.85	$151.90
Purchase #3	$98.25	3.111%	$101.3066	$101.31	$101.30	$101.30
Purchase #4	$116.79	6.105%	$123.92	$123.92	$123.90	$123.90
Purchase #5	$5.40	13.806%	$6.1455	$6.15	$6.15	$6.10
Purchase #6	$150.45	6.186%	$159.7568	$159.76	$159.75	$159.80
Purchase #7	$155.28	8.249%	$168.089	$168.09	$168.10	$168.10
7 purchase totals =	$725.91		$771.8323	$771.84	$771.80	$771.90