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	$147.76	11.327%	$164.4968	$164.50	$164.50	$164.50
Purchase #2	$81.28	7.757%	$87.5849	$87.58	$87.60	$87.60
Purchase #3	$177.43	12.578%	$199.7471	$199.75	$199.75	$199.70
Purchase #4	$32.90	5.149%	$34.594	$34.59	$34.60	$34.60
Purchase #5	$17.57	10.133%	$19.3504	$19.35	$19.35	$19.40
Purchase #6	$100.69	10.600%	$111.3631	$111.36	$111.35	$111.40
Purchase #7	$34.99	6.343%	$37.2094	$37.21	$37.20	$37.20
7 purchase totals =	$592.62		$654.3457	$654.34	$654.35	$654.40