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	$87.55	9.448%	$95.8217	$95.82	$95.80	$95.80
Purchase #2	$141.78	10.264%	$156.3323	$156.33	$156.35	$156.30
Purchase #3	$75.78	10.509%	$83.7437	$83.74	$83.75	$83.70
Purchase #4	$242.96	4.345%	$253.5166	$253.52	$253.50	$253.50
Purchase #5	$56.73	10.164%	$62.496	$62.50	$62.50	$62.50
Purchase #6	$235.54	8.667%	$255.9543	$255.95	$255.95	$256.00
Purchase #7	$61.44	13.480%	$69.7221	$69.72	$69.70	$69.70
7 purchase totals =	$901.78		$977.5867	$977.58	$977.55	$977.50