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	$213.94	8.517%	$232.1613	$232.16	$232.15	$232.20
Purchase #2	$108.99	12.861%	$123.0072	$123.01	$123.00	$123.00
Purchase #3	$79.34	13.693%	$90.204	$90.20	$90.20	$90.20
Purchase #4	$146.67	6.697%	$156.4925	$156.49	$156.50	$156.50
Purchase #5	$85.78	13.618%	$97.4615	$97.46	$97.45	$97.50
Purchase #6	$52.50	13.438%	$59.555	$59.56	$59.55	$59.60
Purchase #7	$22.27	9.804%	$24.4534	$24.45	$24.45	$24.50
7 purchase totals =	$709.49		$783.3349	$783.33	$783.30	$783.50