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	$93.31	11.159%	$103.7225	$103.72	$103.70	$103.70
Purchase #2	$173.78	10.869%	$192.6681	$192.67	$192.65	$192.70
Purchase #3	$155.99	7.828%	$168.2009	$168.20	$168.20	$168.20
Purchase #4	$85.50	4.703%	$89.5211	$89.52	$89.50	$89.50
Purchase #5	$216.99	11.335%	$241.5858	$241.59	$241.60	$241.60
Purchase #6	$94.61	9.769%	$103.8525	$103.85	$103.85	$103.90
Purchase #7	$199.45	11.841%	$223.0669	$223.07	$223.05	$223.10
7 purchase totals =	$1,019.63		$1,122.6178	$1,122.62	$1,122.55	$1,122.70