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	$129.49	6.522%	$137.9353	$137.94	$137.95	$137.90
Purchase #2	$57.94	7.866%	$62.4976	$62.50	$62.50	$62.50
Purchase #3	$21.41	4.632%	$22.4017	$22.40	$22.40	$22.40
Purchase #4	$90.64	8.540%	$98.3807	$98.38	$98.40	$98.40
Purchase #5	$164.73	5.630%	$174.0043	$174.00	$174.00	$174.00
Purchase #6	$20.52	3.467%	$21.2314	$21.23	$21.25	$21.20
Purchase #7	$129.77	6.291%	$137.9338	$137.93	$137.95	$137.90
7 purchase totals =	$614.50		$654.3848	$654.38	$654.45	$654.30