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	$247.30	3.509%	$255.9778	$255.98	$256.00	$256.00
Purchase #2	$245.85	7.271%	$263.7258	$263.73	$263.75	$263.70
Purchase #3	$19.29	13.295%	$21.8546	$21.85	$21.85	$21.90
Purchase #4	$192.45	4.378%	$200.8755	$200.88	$200.90	$200.90
Purchase #5	$217.78	7.230%	$233.5255	$233.53	$233.55	$233.50
Purchase #6	$100.33	11.854%	$112.2231	$112.22	$112.20	$112.20
Purchase #7	$29.37	11.159%	$32.6474	$32.65	$32.65	$32.60
7 purchase totals =	$1,052.37		$1,120.8297	$1,120.84	$1,120.90	$1,120.80