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	$95.44	12.603%	$107.4683	$107.47	$107.45	$107.50
Purchase #2	$16.77	11.206%	$18.6492	$18.65	$18.65	$18.60
Purchase #3	$90.47	11.174%	$100.5791	$100.58	$100.60	$100.60
Purchase #4	$180.33	5.733%	$190.6683	$190.67	$190.65	$190.70
Purchase #5	$103.65	7.811%	$111.7461	$111.75	$111.75	$111.70
Purchase #6	$215.60	12.551%	$242.66	$242.66	$242.65	$242.70
Purchase #7	$215.63	13.239%	$244.1773	$244.18	$244.20	$244.20
7 purchase totals =	$917.89		$1,015.9483	$1,015.96	$1,015.95	$1,016.00