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	$78.70	11.239%	$87.5451	$87.55	$87.55	$87.50
Purchase #2	$126.33	4.861%	$132.4709	$132.47	$132.45	$132.50
Purchase #3	$217.41	6.293%	$231.0916	$231.09	$231.10	$231.10
Purchase #4	$86.76	4.651%	$90.7952	$90.80	$90.80	$90.80
Purchase #5	$95.66	4.704%	$100.1598	$100.16	$100.15	$100.20
Purchase #6	$5.51	4.536%	$5.7599	$5.76	$5.75	$5.80
Purchase #7	$75.52	3.644%	$78.2719	$78.27	$78.25	$78.30
7 purchase totals =	$685.89		$726.0944	$726.10	$726.05	$726.20