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	$155.80	10.642%	$172.3802	$172.38	$172.40	$172.40
Purchase #2	$184.58	11.105%	$205.0776	$205.08	$205.10	$205.10
Purchase #3	$68.79	12.800%	$77.5951	$77.60	$77.60	$77.60
Purchase #4	$158.81	4.267%	$165.5864	$165.59	$165.60	$165.60
Purchase #5	$138.85	9.158%	$151.5659	$151.57	$151.55	$151.60
Purchase #6	$140.56	4.212%	$146.4804	$146.48	$146.50	$146.50
Purchase #7	$160.53	4.109%	$167.1262	$167.13	$167.15	$167.10
7 purchase totals =	$1,007.92		$1,085.8118	$1,085.83	$1,085.90	$1,085.90