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	$67.85	13.294%	$76.87	$76.87	$76.85	$76.90
Purchase #2	$35.99	7.325%	$38.6263	$38.63	$38.65	$38.60
Purchase #3	$129.89	11.680%	$145.0612	$145.06	$145.05	$145.10
Purchase #4	$10.53	8.804%	$11.4571	$11.46	$11.45	$11.50
Purchase #5	$81.31	9.636%	$89.145	$89.15	$89.15	$89.10
Purchase #6	$87.83	8.317%	$95.1348	$95.13	$95.15	$95.10
Purchase #7	$133.74	5.677%	$141.3324	$141.33	$141.35	$141.30
7 purchase totals =	$547.14		$597.6268	$597.63	$597.65	$597.60