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	$55.64	9.259%	$60.7917	$60.79	$60.80	$60.80
Purchase #2	$144.83	4.371%	$151.1605	$151.16	$151.15	$151.20
Purchase #3	$38.42	5.506%	$40.5354	$40.54	$40.55	$40.50
Purchase #4	$70.93	10.287%	$78.2266	$78.23	$78.25	$78.20
Purchase #5	$171.66	4.187%	$178.8474	$178.85	$178.85	$178.80
Purchase #6	$90.46	7.868%	$97.5774	$97.58	$97.60	$97.60
Purchase #7	$15.95	9.232%	$17.4225	$17.42	$17.40	$17.40
7 purchase totals =	$587.89		$624.5615	$624.57	$624.60	$624.50