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	$162.48	12.230%	$182.3513	$182.35	$182.35	$182.40
Purchase #2	$217.29	10.721%	$240.5857	$240.59	$240.60	$240.60
Purchase #3	$152.43	13.163%	$172.4944	$172.49	$172.50	$172.50
Purchase #4	$77.95	5.210%	$82.0112	$82.01	$82.00	$82.00
Purchase #5	$161.38	3.785%	$167.4882	$167.49	$167.50	$167.50
Purchase #6	$228.37	3.861%	$237.1874	$237.19	$237.20	$237.20
Purchase #7	$15.83	11.873%	$17.7095	$17.71	$17.70	$17.70
7 purchase totals =	$1,015.73		$1,099.8277	$1,099.83	$1,099.85	$1,099.90