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	$155.88	10.330%	$171.9824	$171.98	$172.00	$172.00
Purchase #2	$76.50	6.206%	$81.2476	$81.25	$81.25	$81.20
Purchase #3	$102.29	13.765%	$116.3702	$116.37	$116.35	$116.40
Purchase #4	$78.59	3.802%	$81.578	$81.58	$81.60	$81.60
Purchase #5	$92.98	6.530%	$99.0516	$99.05	$99.05	$99.10
Purchase #6	$223.42	11.660%	$249.4708	$249.47	$249.45	$249.50
Purchase #7	$77.49	7.587%	$83.3692	$83.37	$83.35	$83.40
7 purchase totals =	$807.15		$883.0698	$883.07	$883.05	$883.20