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	$197.88	5.755%	$209.268	$209.27	$209.25	$209.30
Purchase #2	$112.68	9.488%	$123.3711	$123.37	$123.35	$123.40
Purchase #3	$247.46	13.360%	$280.5207	$280.52	$280.50	$280.50
Purchase #4	$45.38	13.343%	$51.4351	$51.44	$51.45	$51.40
Purchase #5	$38.25	7.153%	$40.986	$40.99	$41.00	$41.00
Purchase #6	$54.32	5.620%	$57.3728	$57.37	$57.35	$57.40
Purchase #7	$121.52	9.387%	$132.9271	$132.93	$132.95	$132.90
7 purchase totals =	$817.49		$895.8808	$895.89	$895.85	$895.90