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	$61.83	4.128%	$64.3823	$64.38	$64.40	$64.40
Purchase #2	$10.99	8.491%	$11.9232	$11.92	$11.90	$11.90
Purchase #3	$34.76	10.669%	$38.4685	$38.47	$38.45	$38.50
Purchase #4	$5.67	6.375%	$6.0315	$6.03	$6.05	$6.00
Purchase #5	$87.98	13.624%	$99.9664	$99.97	$99.95	$100.00
Purchase #6	$11.50	12.445%	$12.9312	$12.93	$12.95	$12.90
Purchase #7	$150.49	13.748%	$171.1794	$171.18	$171.20	$171.20
7 purchase totals =	$363.22		$404.8825	$404.88	$404.90	$404.90