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	$88.32	7.324%	$94.7886	$94.79	$94.80	$94.80
Purchase #2	$92.42	13.610%	$104.9984	$105.00	$105.00	$105.00
Purchase #3	$31.46	12.872%	$35.5095	$35.51	$35.50	$35.50
Purchase #4	$30.66	11.512%	$34.1896	$34.19	$34.20	$34.20
Purchase #5	$215.84	11.742%	$241.1839	$241.18	$241.20	$241.20
Purchase #6	$46.37	4.239%	$48.3356	$48.34	$48.35	$48.30
Purchase #7	$95.46	13.574%	$108.4177	$108.42	$108.40	$108.40
7 purchase totals =	$600.53		$667.4233	$667.43	$667.45	$667.40