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	$53.77	3.622%	$55.7175	$55.72	$55.70	$55.70
Purchase #2	$18.61	5.269%	$19.5906	$19.59	$19.60	$19.60
Purchase #3	$14.32	11.516%	$15.9691	$15.97	$15.95	$16.00
Purchase #4	$133.47	11.529%	$148.8578	$148.86	$148.85	$148.90
Purchase #5	$90.99	10.721%	$100.745	$100.75	$100.75	$100.70
Purchase #6	$141.81	13.603%	$161.1004	$161.10	$161.10	$161.10
Purchase #7	$247.81	9.712%	$271.8773	$271.88	$271.90	$271.90
7 purchase totals =	$700.78		$773.8577	$773.87	$773.85	$773.90