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	$43.52	7.327%	$46.7087	$46.71	$46.70	$46.70
Purchase #2	$42.85	7.140%	$45.9095	$45.91	$45.90	$45.90
Purchase #3	$87.87	10.509%	$97.1043	$97.10	$97.10	$97.10
Purchase #4	$143.70	6.494%	$153.0319	$153.03	$153.05	$153.00
Purchase #5	$100.78	13.503%	$114.3883	$114.39	$114.40	$114.40
Purchase #6	$109.99	12.267%	$123.4825	$123.48	$123.50	$123.50
Purchase #7	$85.45	11.303%	$95.1084	$95.11	$95.10	$95.10
7 purchase totals =	$614.16		$675.7336	$675.73	$675.75	$675.70