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	$242.54	5.761%	$256.5127	$256.51	$256.50	$256.50
Purchase #2	$177.59	3.301%	$183.4522	$183.45	$183.45	$183.50
Purchase #3	$219.67	3.754%	$227.9164	$227.92	$227.90	$227.90
Purchase #4	$94.38	6.855%	$100.8497	$100.85	$100.85	$100.80
Purchase #5	$30.98	4.669%	$32.4265	$32.43	$32.45	$32.40
Purchase #6	$164.94	11.557%	$184.0021	$184.00	$184.00	$184.00
Purchase #7	$186.42	7.456%	$200.3195	$200.32	$200.30	$200.30
7 purchase totals =	$1,116.52		$1,185.4791	$1,185.48	$1,185.45	$1,185.40