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	$59.88	9.462%	$65.5458	$65.55	$65.55	$65.50
Purchase #2	$184.54	3.193%	$190.4324	$190.43	$190.45	$190.40
Purchase #3	$29.75	13.385%	$33.732	$33.73	$33.75	$33.70
Purchase #4	$43.87	4.509%	$45.8481	$45.85	$45.85	$45.80
Purchase #5	$108.74	9.274%	$118.8245	$118.82	$118.80	$118.80
Purchase #6	$104.88	4.752%	$109.8639	$109.86	$109.85	$109.90
Purchase #7	$148.29	3.613%	$153.6477	$153.65	$153.65	$153.60
7 purchase totals =	$679.95		$717.8944	$717.89	$717.90	$717.70