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	$76.97	10.826%	$85.3028	$85.30	$85.30	$85.30
Purchase #2	$136.65	4.313%	$142.5437	$142.54	$142.55	$142.50
Purchase #3	$192.87	11.553%	$215.1523	$215.15	$215.15	$215.20
Purchase #4	$201.27	13.707%	$228.8581	$228.86	$228.85	$228.90
Purchase #5	$90.80	10.579%	$100.4057	$100.41	$100.40	$100.40
Purchase #6	$163.75	5.151%	$172.1848	$172.18	$172.20	$172.20
Purchase #7	$125.91	5.509%	$132.8464	$132.85	$132.85	$132.80
7 purchase totals =	$988.22		$1,077.2938	$1,077.29	$1,077.30	$1,077.30