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	$37.64	7.176%	$40.341	$40.34	$40.35	$40.30
Purchase #2	$188.32	5.494%	$198.6663	$198.67	$198.65	$198.70
Purchase #3	$59.95	5.789%	$63.4205	$63.42	$63.40	$63.40
Purchase #4	$184.29	7.156%	$197.4778	$197.48	$197.50	$197.50
Purchase #5	$101.78	7.346%	$109.2568	$109.26	$109.25	$109.30
Purchase #6	$57.75	13.789%	$65.7131	$65.71	$65.70	$65.70
Purchase #7	$88.83	13.383%	$100.7181	$100.72	$100.70	$100.70
7 purchase totals =	$718.56		$775.5936	$775.60	$775.55	$775.60