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	$102.35	3.247%	$105.6733	$105.67	$105.65	$105.70
Purchase #2	$235.75	12.141%	$264.3724	$264.37	$264.35	$264.40
Purchase #3	$6.83	5.812%	$7.227	$7.23	$7.25	$7.20
Purchase #4	$6.62	11.302%	$7.3682	$7.37	$7.35	$7.40
Purchase #5	$29.78	11.776%	$33.2869	$33.29	$33.30	$33.30
Purchase #6	$65.53	11.859%	$73.3012	$73.30	$73.30	$73.30
Purchase #7	$124.45	5.739%	$131.5922	$131.59	$131.60	$131.60
7 purchase totals =	$571.31		$622.8212	$622.82	$622.80	$622.90