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	$144.27	10.517%	$159.4429	$159.44	$159.45	$159.40
Purchase #2	$34.86	3.261%	$35.9968	$36.00	$36.00	$36.00
Purchase #3	$233.32	9.705%	$255.9637	$255.96	$255.95	$256.00
Purchase #4	$68.49	3.735%	$71.0481	$71.05	$71.05	$71.00
Purchase #5	$80.75	8.433%	$87.5596	$87.56	$87.55	$87.60
Purchase #6	$43.54	4.443%	$45.4745	$45.47	$45.45	$45.50
Purchase #7	$60.70	8.831%	$66.0604	$66.06	$66.05	$66.10
7 purchase totals =	$665.93		$721.5460	$721.54	$721.50	$721.60