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	$235.72	11.256%	$262.2526	$262.25	$262.25	$262.30
Purchase #2	$89.67	5.407%	$94.5185	$94.52	$94.50	$94.50
Purchase #3	$107.75	8.605%	$117.0219	$117.02	$117.00	$117.00
Purchase #4	$157.72	13.449%	$178.9318	$178.93	$178.95	$178.90
Purchase #5	$103.52	11.528%	$115.4538	$115.45	$115.45	$115.50
Purchase #6	$145.82	3.492%	$150.912	$150.91	$150.90	$150.90
Purchase #7	$35.74	6.135%	$37.9326	$37.93	$37.95	$37.90
7 purchase totals =	$875.94		$957.0232	$957.01	$957.00	$957.00