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	$54.39	8.861%	$59.2095	$59.21	$59.20	$59.20
Purchase #2	$7.72	13.383%	$8.7532	$8.75	$8.75	$8.80
Purchase #3	$157.98	12.380%	$177.5379	$177.54	$177.55	$177.50
Purchase #4	$81.86	10.794%	$90.696	$90.70	$90.70	$90.70
Purchase #5	$132.56	10.528%	$146.5159	$146.52	$146.50	$146.50
Purchase #6	$82.81	4.826%	$86.8064	$86.81	$86.80	$86.80
Purchase #7	$124.74	11.319%	$138.8593	$138.86	$138.85	$138.90
7 purchase totals =	$642.06		$708.3782	$708.39	$708.35	$708.40