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	$146.77	10.559%	$162.2674	$162.27	$162.25	$162.30
Purchase #2	$66.57	3.504%	$68.9026	$68.90	$68.90	$68.90
Purchase #3	$238.97	10.395%	$263.8109	$263.81	$263.80	$263.80
Purchase #4	$19.27	8.663%	$20.9394	$20.94	$20.95	$20.90
Purchase #5	$37.56	4.389%	$39.2085	$39.21	$39.20	$39.20
Purchase #6	$37.77	7.495%	$40.6009	$40.60	$40.60	$40.60
Purchase #7	$30.28	11.164%	$33.6605	$33.66	$33.65	$33.70
7 purchase totals =	$577.19		$629.3902	$629.39	$629.35	$629.40