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	$155.30	8.492%	$168.4881	$168.49	$168.50	$168.50
Purchase #2	$11.30	13.555%	$12.8317	$12.83	$12.85	$12.80
Purchase #3	$99.78	4.519%	$104.2891	$104.29	$104.30	$104.30
Purchase #4	$53.35	9.833%	$58.5959	$58.60	$58.60	$58.60
Purchase #5	$175.48	6.308%	$186.5493	$186.55	$186.55	$186.50
Purchase #6	$153.53	12.121%	$172.1394	$172.14	$172.15	$172.10
Purchase #7	$28.42	3.107%	$29.303	$29.30	$29.30	$29.30
7 purchase totals =	$677.16		$732.1965	$732.20	$732.25	$732.10