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	$59.89	9.692%	$65.6945	$65.69	$65.70	$65.70
Purchase #2	$164.43	12.835%	$185.5346	$185.53	$185.55	$185.50
Purchase #3	$9.45	10.325%	$10.4257	$10.43	$10.45	$10.40
Purchase #4	$31.49	9.262%	$34.4066	$34.41	$34.40	$34.40
Purchase #5	$190.68	12.756%	$215.0031	$215.00	$215.00	$215.00
Purchase #6	$249.82	10.314%	$275.5864	$275.59	$275.60	$275.60
Purchase #7	$238.77	7.420%	$256.4867	$256.49	$256.50	$256.50
7 purchase totals =	$944.53		$1,043.1376	$1,043.14	$1,043.20	$1,043.10