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	$244.32	8.656%	$265.4683	$265.47	$265.45	$265.50
Purchase #2	$50.53	6.727%	$53.9292	$53.93	$53.95	$53.90
Purchase #3	$239.26	7.372%	$256.8982	$256.90	$256.90	$256.90
Purchase #4	$201.40	10.114%	$221.7696	$221.77	$221.75	$221.80
Purchase #5	$29.67	9.567%	$32.5085	$32.51	$32.50	$32.50
Purchase #6	$126.72	12.536%	$142.6056	$142.61	$142.60	$142.60
Purchase #7	$22.31	11.307%	$24.8326	$24.83	$24.85	$24.80
7 purchase totals =	$914.21		$998.0120	$998.02	$998.00	$998.00