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	$63.28	7.816%	$68.226	$68.23	$68.25	$68.20
Purchase #2	$115.42	10.415%	$127.441	$127.44	$127.45	$127.40
Purchase #3	$83.57	13.174%	$94.5795	$94.58	$94.60	$94.60
Purchase #4	$33.85	10.139%	$37.2821	$37.28	$37.30	$37.30
Purchase #5	$48.86	5.457%	$51.5263	$51.53	$51.55	$51.50
Purchase #6	$173.42	7.752%	$186.8635	$186.86	$186.85	$186.90
Purchase #7	$202.82	3.466%	$209.8497	$209.85	$209.85	$209.80
7 purchase totals =	$721.22		$775.7681	$775.77	$775.85	$775.70