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	$76.75	12.858%	$86.6185	$86.62	$86.60	$86.60
Purchase #2	$137.46	11.528%	$153.3064	$153.31	$153.30	$153.30
Purchase #3	$100.45	10.738%	$111.2363	$111.24	$111.25	$111.20
Purchase #4	$87.29	3.230%	$90.1095	$90.11	$90.10	$90.10
Purchase #5	$119.88	6.645%	$127.846	$127.85	$127.85	$127.80
Purchase #6	$122.73	4.378%	$128.1031	$128.10	$128.10	$128.10
Purchase #7	$17.43	8.133%	$18.8476	$18.85	$18.85	$18.80
7 purchase totals =	$661.99		$716.0674	$716.08	$716.05	$715.90