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	$32.93	6.163%	$34.9595	$34.96	$34.95	$35.00
Purchase #2	$10.59	3.313%	$10.9408	$10.94	$10.95	$10.90
Purchase #3	$150.47	6.747%	$160.6222	$160.62	$160.60	$160.60
Purchase #4	$224.56	11.557%	$250.5124	$250.51	$250.50	$250.50
Purchase #5	$211.80	9.782%	$232.5183	$232.52	$232.50	$232.50
Purchase #6	$66.29	9.293%	$72.4503	$72.45	$72.45	$72.50
Purchase #7	$199.78	4.507%	$208.7841	$208.78	$208.80	$208.80
7 purchase totals =	$896.42		$970.7876	$970.78	$970.75	$970.80