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	$7.45	13.530%	$8.458	$8.46	$8.45	$8.50
Purchase #2	$75.62	3.868%	$78.545	$78.55	$78.55	$78.50
Purchase #3	$111.72	4.835%	$117.1217	$117.12	$117.10	$117.10
Purchase #4	$58.83	3.385%	$60.8214	$60.82	$60.80	$60.80
Purchase #5	$153.60	11.661%	$171.5113	$171.51	$171.50	$171.50
Purchase #6	$87.79	3.147%	$90.5528	$90.55	$90.55	$90.60
Purchase #7	$195.87	3.230%	$202.1966	$202.20	$202.20	$202.20
7 purchase totals =	$690.88		$729.2068	$729.21	$729.15	$729.20