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	$116.71	8.689%	$126.8509	$126.85	$126.85	$126.90
Purchase #2	$31.85	8.249%	$34.4773	$34.48	$34.50	$34.50
Purchase #3	$105.28	6.175%	$111.781	$111.78	$111.80	$111.80
Purchase #4	$120.29	13.544%	$136.5821	$136.58	$136.60	$136.60
Purchase #5	$204.57	6.220%	$217.2943	$217.29	$217.30	$217.30
Purchase #6	$161.51	11.429%	$179.969	$179.97	$179.95	$180.00
Purchase #7	$143.78	5.314%	$151.4205	$151.42	$151.40	$151.40
7 purchase totals =	$883.99		$958.3751	$958.37	$958.40	$958.50