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	$128.62	13.518%	$146.0069	$146.01	$146.00	$146.00
Purchase #2	$50.71	10.350%	$55.9585	$55.96	$55.95	$56.00
Purchase #3	$71.89	7.377%	$77.1933	$77.19	$77.20	$77.20
Purchase #4	$90.86	8.833%	$98.8857	$98.89	$98.90	$98.90
Purchase #5	$177.42	11.640%	$198.0717	$198.07	$198.05	$198.10
Purchase #6	$16.54	11.549%	$18.4502	$18.45	$18.45	$18.50
Purchase #7	$127.36	11.346%	$141.8103	$141.81	$141.80	$141.80
7 purchase totals =	$663.40		$736.3766	$736.38	$736.35	$736.50