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	$124.99	5.618%	$132.0119	$132.01	$132.00	$132.00
Purchase #2	$241.68	10.177%	$266.2758	$266.28	$266.30	$266.30
Purchase #3	$77.53	6.554%	$82.6113	$82.61	$82.60	$82.60
Purchase #4	$152.84	13.763%	$173.8754	$173.88	$173.90	$173.90
Purchase #5	$97.31	7.397%	$104.508	$104.51	$104.50	$104.50
Purchase #6	$44.69	4.111%	$46.5272	$46.53	$46.55	$46.50
Purchase #7	$76.60	9.443%	$83.8333	$83.83	$83.85	$83.80
7 purchase totals =	$815.64		$889.6429	$889.65	$889.70	$889.60