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	$175.91	9.490%	$192.6039	$192.60	$192.60	$192.60
Purchase #2	$127.52	3.604%	$132.1158	$132.12	$132.10	$132.10
Purchase #3	$113.78	3.801%	$118.1048	$118.10	$118.10	$118.10
Purchase #4	$11.28	13.246%	$12.7741	$12.77	$12.75	$12.80
Purchase #5	$170.32	7.575%	$183.2217	$183.22	$183.20	$183.20
Purchase #6	$95.25	5.154%	$100.1592	$100.16	$100.15	$100.20
Purchase #7	$80.29	4.523%	$83.9215	$83.92	$83.90	$83.90
7 purchase totals =	$774.35		$822.9010	$822.89	$822.80	$822.90