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	$223.92	8.333%	$242.5793	$242.58	$242.60	$242.60
Purchase #2	$192.56	12.778%	$217.1653	$217.17	$217.15	$217.20
Purchase #3	$9.30	12.765%	$10.4871	$10.49	$10.50	$10.50
Purchase #4	$72.63	7.404%	$78.0075	$78.01	$78.00	$78.00
Purchase #5	$79.73	9.233%	$87.0915	$87.09	$87.10	$87.10
Purchase #6	$166.99	10.455%	$184.4488	$184.45	$184.45	$184.40
Purchase #7	$241.45	5.838%	$255.5459	$255.55	$255.55	$255.50
7 purchase totals =	$986.58		$1,075.3254	$1,075.34	$1,075.35	$1,075.30