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	$27.72	6.839%	$29.6158	$29.62	$29.60	$29.60
Purchase #2	$170.75	11.143%	$189.7767	$189.78	$189.80	$189.80
Purchase #3	$68.30	6.492%	$72.734	$72.73	$72.75	$72.70
Purchase #4	$238.32	10.278%	$262.8145	$262.81	$262.80	$262.80
Purchase #5	$144.72	5.493%	$152.6695	$152.67	$152.65	$152.70
Purchase #6	$148.29	6.322%	$157.6649	$157.66	$157.65	$157.70
Purchase #7	$138.53	10.455%	$153.0133	$153.01	$153.00	$153.00
7 purchase totals =	$936.63		$1,018.2887	$1,018.28	$1,018.25	$1,018.30