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	$109.43	9.224%	$119.5238	$119.52	$119.50	$119.50
Purchase #2	$215.93	4.438%	$225.513	$225.51	$225.50	$225.50
Purchase #3	$25.49	11.166%	$28.3362	$28.34	$28.35	$28.30
Purchase #4	$123.77	7.123%	$132.5861	$132.59	$132.60	$132.60
Purchase #5	$23.35	11.429%	$26.0187	$26.02	$26.00	$26.00
Purchase #6	$70.34	11.567%	$78.4762	$78.48	$78.50	$78.50
Purchase #7	$244.48	5.231%	$257.2687	$257.27	$257.25	$257.30
7 purchase totals =	$812.79		$867.7227	$867.73	$867.70	$867.70