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	$167.46	3.346%	$173.0632	$173.06	$173.05	$173.10
Purchase #2	$241.57	10.871%	$267.8311	$267.83	$267.85	$267.80
Purchase #3	$146.86	11.472%	$163.7078	$163.71	$163.70	$163.70
Purchase #4	$138.64	11.833%	$155.0453	$155.05	$155.05	$155.00
Purchase #5	$52.96	6.835%	$56.5798	$56.58	$56.60	$56.60
Purchase #6	$220.70	11.125%	$245.2529	$245.25	$245.25	$245.30
Purchase #7	$99.64	11.644%	$111.2421	$111.24	$111.25	$111.20
7 purchase totals =	$1,067.83		$1,172.7222	$1,172.72	$1,172.75	$1,172.70