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	$66.81	10.630%	$73.9119	$73.91	$73.90	$73.90
Purchase #2	$13.87	11.508%	$15.4662	$15.47	$15.45	$15.50
Purchase #3	$76.69	7.686%	$82.5844	$82.58	$82.60	$82.60
Purchase #4	$17.60	5.152%	$18.5068	$18.51	$18.50	$18.50
Purchase #5	$234.50	4.505%	$245.0642	$245.06	$245.05	$245.10
Purchase #6	$233.95	11.674%	$261.2613	$261.26	$261.25	$261.30
Purchase #7	$12.89	5.233%	$13.5645	$13.56	$13.55	$13.60
7 purchase totals =	$656.31		$710.3593	$710.35	$710.30	$710.50