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	$107.68	3.813%	$111.7858	$111.79	$111.80	$111.80
Purchase #2	$83.59	10.124%	$92.0527	$92.05	$92.05	$92.10
Purchase #3	$20.84	3.173%	$21.5013	$21.50	$21.50	$21.50
Purchase #4	$245.31	4.395%	$256.0914	$256.09	$256.10	$256.10
Purchase #5	$78.28	11.633%	$87.3863	$87.39	$87.40	$87.40
Purchase #6	$144.93	7.721%	$156.12	$156.12	$156.10	$156.10
Purchase #7	$215.66	8.169%	$233.2773	$233.28	$233.30	$233.30
7 purchase totals =	$896.29		$958.2148	$958.22	$958.25	$958.30