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	$250.81	4.704%	$262.6081	$262.61	$262.60	$262.60
Purchase #2	$32.78	10.110%	$36.0941	$36.09	$36.10	$36.10
Purchase #3	$119.91	9.326%	$131.0928	$131.09	$131.10	$131.10
Purchase #4	$187.60	4.413%	$195.8788	$195.88	$195.90	$195.90
Purchase #5	$114.55	7.482%	$123.1206	$123.12	$123.10	$123.10
Purchase #6	$30.78	13.509%	$34.9381	$34.94	$34.95	$34.90
Purchase #7	$10.52	3.554%	$10.8939	$10.89	$10.90	$10.90
7 purchase totals =	$746.95		$794.6264	$794.62	$794.65	$794.60