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	$12.96	8.117%	$14.012	$14.01	$14.00	$14.00
Purchase #2	$28.78	3.321%	$29.7358	$29.74	$29.75	$29.70
Purchase #3	$178.93	12.141%	$200.6539	$200.65	$200.65	$200.70
Purchase #4	$15.86	12.803%	$17.8906	$17.89	$17.90	$17.90
Purchase #5	$111.68	4.754%	$116.9893	$116.99	$117.00	$117.00
Purchase #6	$81.60	10.307%	$90.0105	$90.01	$90.00	$90.00
Purchase #7	$83.58	8.340%	$90.5506	$90.55	$90.55	$90.60
7 purchase totals =	$513.39		$559.8427	$559.84	$559.85	$559.90