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	$205.79	12.334%	$231.1721	$231.17	$231.15	$231.20
Purchase #2	$91.45	4.439%	$95.5095	$95.51	$95.50	$95.50
Purchase #3	$90.66	7.102%	$97.0987	$97.10	$97.10	$97.10
Purchase #4	$63.34	11.419%	$70.5728	$70.57	$70.55	$70.60
Purchase #5	$106.95	10.171%	$117.8279	$117.83	$117.85	$117.80
Purchase #6	$116.78	5.646%	$123.3734	$123.37	$123.35	$123.40
Purchase #7	$6.32	9.558%	$6.9241	$6.92	$6.90	$6.90
7 purchase totals =	$681.29		$742.4785	$742.47	$742.40	$742.50