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	$164.50	8.120%	$177.8574	$177.86	$177.85	$177.90
Purchase #2	$93.71	5.116%	$98.5042	$98.50	$98.50	$98.50
Purchase #3	$173.89	9.548%	$190.493	$190.49	$190.50	$190.50
Purchase #4	$54.34	9.358%	$59.4251	$59.43	$59.45	$59.40
Purchase #5	$54.32	10.257%	$59.8916	$59.89	$59.90	$59.90
Purchase #6	$136.99	9.527%	$150.041	$150.04	$150.05	$150.00
Purchase #7	$9.47	8.516%	$10.2765	$10.28	$10.30	$10.30
7 purchase totals =	$687.22		$746.4888	$746.49	$746.55	$746.50