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	$103.95	5.744%	$109.9209	$109.92	$109.90	$109.90
Purchase #2	$215.83	8.858%	$234.9482	$234.95	$234.95	$234.90
Purchase #3	$95.72	9.421%	$104.7378	$104.74	$104.75	$104.70
Purchase #4	$90.92	10.483%	$100.4511	$100.45	$100.45	$100.50
Purchase #5	$69.38	12.479%	$78.0379	$78.04	$78.05	$78.00
Purchase #6	$227.82	4.324%	$237.6709	$237.67	$237.65	$237.70
Purchase #7	$69.83	13.264%	$79.0923	$79.09	$79.10	$79.10
7 purchase totals =	$873.45		$944.8591	$944.86	$944.85	$944.80