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	$40.42	6.495%	$43.0453	$43.05	$43.05	$43.00
Purchase #2	$153.88	12.252%	$172.7334	$172.73	$172.75	$172.70
Purchase #3	$200.45	7.558%	$215.6	$215.60	$215.60	$215.60
Purchase #4	$25.92	7.367%	$27.8295	$27.83	$27.85	$27.80
Purchase #5	$66.27	10.283%	$73.0845	$73.08	$73.10	$73.10
Purchase #6	$27.52	3.820%	$28.5713	$28.57	$28.55	$28.60
Purchase #7	$142.59	7.847%	$153.779	$153.78	$153.80	$153.80
7 purchase totals =	$657.05		$714.6430	$714.64	$714.70	$714.60