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	$170.88	8.252%	$184.981	$184.98	$185.00	$185.00
Purchase #2	$137.66	4.709%	$144.1424	$144.14	$144.15	$144.10
Purchase #3	$99.48	12.208%	$111.6245	$111.62	$111.60	$111.60
Purchase #4	$105.85	11.645%	$118.1762	$118.18	$118.20	$118.20
Purchase #5	$80.56	5.753%	$85.1946	$85.19	$85.20	$85.20
Purchase #6	$213.36	6.189%	$226.5649	$226.56	$226.55	$226.60
Purchase #7	$204.92	10.707%	$226.8608	$226.86	$226.85	$226.90
7 purchase totals =	$1,012.71		$1,097.5444	$1,097.53	$1,097.55	$1,097.60