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	$215.82	10.278%	$238.002	$238.00	$238.00	$238.00
Purchase #2	$85.90	5.578%	$90.6915	$90.69	$90.70	$90.70
Purchase #3	$38.93	13.350%	$44.1272	$44.13	$44.15	$44.10
Purchase #4	$37.91	13.266%	$42.9391	$42.94	$42.95	$42.90
Purchase #5	$117.70	12.800%	$132.7656	$132.77	$132.75	$132.80
Purchase #6	$70.78	5.308%	$74.537	$74.54	$74.55	$74.50
Purchase #7	$10.86	9.334%	$11.8737	$11.87	$11.85	$11.90
7 purchase totals =	$577.90		$634.9361	$634.94	$634.95	$634.90