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	$10.33	9.321%	$11.2929	$11.29	$11.30	$11.30
Purchase #2	$232.93	5.392%	$245.4896	$245.49	$245.50	$245.50
Purchase #3	$192.65	3.130%	$198.6799	$198.68	$198.70	$198.70
Purchase #4	$90.60	4.409%	$94.5946	$94.59	$94.60	$94.60
Purchase #5	$118.34	11.679%	$132.1609	$132.16	$132.15	$132.20
Purchase #6	$196.92	7.573%	$211.8328	$211.83	$211.85	$211.80
Purchase #7	$138.38	7.262%	$148.4292	$148.43	$148.45	$148.40
7 purchase totals =	$980.15		$1,042.4799	$1,042.47	$1,042.55	$1,042.50