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	$240.79	7.352%	$258.4929	$258.49	$258.50	$258.50
Purchase #2	$178.45	11.799%	$199.5053	$199.51	$199.50	$199.50
Purchase #3	$79.62	10.257%	$87.7866	$87.79	$87.80	$87.80
Purchase #4	$80.75	12.617%	$90.9382	$90.94	$90.95	$90.90
Purchase #5	$120.47	10.307%	$132.8868	$132.89	$132.90	$132.90
Purchase #6	$80.85	13.737%	$91.9564	$91.96	$91.95	$92.00
Purchase #7	$84.92	9.439%	$92.9356	$92.94	$92.95	$92.90
7 purchase totals =	$865.85		$954.5018	$954.52	$954.55	$954.50