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	$53.66	12.366%	$60.2956	$60.30	$60.30	$60.30
Purchase #2	$61.78	5.808%	$65.3682	$65.37	$65.35	$65.40
Purchase #3	$231.29	10.239%	$254.9718	$254.97	$254.95	$255.00
Purchase #4	$36.25	12.638%	$40.8313	$40.83	$40.85	$40.80
Purchase #5	$132.34	7.854%	$142.734	$142.73	$142.75	$142.70
Purchase #6	$250.71	6.278%	$266.4496	$266.45	$266.45	$266.40
Purchase #7	$214.38	5.241%	$225.6157	$225.62	$225.60	$225.60
7 purchase totals =	$980.41		$1,056.2662	$1,056.27	$1,056.25	$1,056.20