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	$61.32	9.540%	$67.1699	$67.17	$67.15	$67.20
Purchase #2	$6.57	9.738%	$7.2098	$7.21	$7.20	$7.20
Purchase #3	$145.36	10.304%	$160.3379	$160.34	$160.35	$160.30
Purchase #4	$72.61	5.527%	$76.6232	$76.62	$76.60	$76.60
Purchase #5	$224.59	4.582%	$234.8807	$234.88	$234.90	$234.90
Purchase #6	$118.44	7.584%	$127.4225	$127.42	$127.40	$127.40
Purchase #7	$120.60	5.660%	$127.426	$127.43	$127.45	$127.40
7 purchase totals =	$749.49		$801.0700	$801.07	$801.05	$801.00