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	$113.28	8.716%	$123.1535	$123.15	$123.15	$123.20
Purchase #2	$161.47	10.343%	$178.1708	$178.17	$178.15	$178.20
Purchase #3	$65.93	11.401%	$73.4467	$73.45	$73.45	$73.40
Purchase #4	$197.84	4.430%	$206.6043	$206.60	$206.60	$206.60
Purchase #5	$178.68	6.429%	$190.1673	$190.17	$190.15	$190.20
Purchase #6	$215.74	7.462%	$231.8385	$231.84	$231.85	$231.80
Purchase #7	$74.85	4.543%	$78.2504	$78.25	$78.25	$78.30
7 purchase totals =	$1,007.79		$1,081.6315	$1,081.63	$1,081.60	$1,081.70