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	$78.35	10.561%	$86.6245	$86.62	$86.60	$86.60
Purchase #2	$13.54	9.853%	$14.8741	$14.87	$14.85	$14.90
Purchase #3	$37.35	9.491%	$40.8949	$40.89	$40.90	$40.90
Purchase #4	$103.52	12.868%	$116.841	$116.84	$116.85	$116.80
Purchase #5	$90.32	11.538%	$100.7411	$100.74	$100.75	$100.70
Purchase #6	$97.97	10.676%	$108.4293	$108.43	$108.45	$108.40
Purchase #7	$80.98	13.604%	$91.9965	$92.00	$92.00	$92.00
7 purchase totals =	$502.03		$560.4014	$560.39	$560.40	$560.30