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	$172.86	5.412%	$182.2152	$182.22	$182.20	$182.20
Purchase #2	$22.80	6.123%	$24.196	$24.20	$24.20	$24.20
Purchase #3	$96.52	8.179%	$104.4144	$104.41	$104.40	$104.40
Purchase #4	$145.49	5.453%	$153.4236	$153.42	$153.40	$153.40
Purchase #5	$102.79	8.438%	$111.4634	$111.46	$111.45	$111.50
Purchase #6	$137.79	12.757%	$155.3679	$155.37	$155.35	$155.40
Purchase #7	$88.47	3.514%	$91.5788	$91.58	$91.60	$91.60
7 purchase totals =	$766.72		$822.6593	$822.66	$822.60	$822.70