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	$48.47	10.133%	$53.3815	$53.38	$53.40	$53.40
Purchase #2	$111.61	4.316%	$116.4271	$116.43	$116.45	$116.40
Purchase #3	$84.90	10.721%	$94.0021	$94.00	$94.00	$94.00
Purchase #4	$80.87	12.422%	$90.9157	$90.92	$90.90	$90.90
Purchase #5	$54.32	3.862%	$56.4178	$56.42	$56.40	$56.40
Purchase #6	$14.25	11.318%	$15.8628	$15.86	$15.85	$15.90
Purchase #7	$125.57	12.333%	$141.0565	$141.06	$141.05	$141.10
7 purchase totals =	$519.99		$568.0635	$568.07	$568.05	$568.10