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	$226.79	9.311%	$247.9064	$247.91	$247.90	$247.90
Purchase #2	$31.41	4.508%	$32.826	$32.83	$32.85	$32.80
Purchase #3	$100.50	8.349%	$108.8907	$108.89	$108.90	$108.90
Purchase #4	$83.66	13.450%	$94.9123	$94.91	$94.90	$94.90
Purchase #5	$225.98	7.429%	$242.7681	$242.77	$242.75	$242.80
Purchase #6	$241.69	10.305%	$266.5962	$266.60	$266.60	$266.60
Purchase #7	$17.31	3.865%	$17.979	$17.98	$18.00	$18.00
7 purchase totals =	$927.34		$1,011.8787	$1,011.89	$1,011.90	$1,011.90