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	$216.33	4.249%	$225.5219	$225.52	$225.50	$225.50
Purchase #2	$41.65	8.261%	$45.0907	$45.09	$45.10	$45.10
Purchase #3	$207.74	11.870%	$232.3987	$232.40	$232.40	$232.40
Purchase #4	$246.43	13.456%	$279.5896	$279.59	$279.60	$279.60
Purchase #5	$226.38	6.870%	$241.9323	$241.93	$241.95	$241.90
Purchase #6	$43.93	4.402%	$45.8638	$45.86	$45.85	$45.90
Purchase #7	$198.76	11.716%	$222.0467	$222.05	$222.05	$222.00
7 purchase totals =	$1,181.22		$1,292.4437	$1,292.44	$1,292.45	$1,292.40