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	$244.30	4.795%	$256.0142	$256.01	$256.00	$256.00
Purchase #2	$154.68	5.345%	$162.9476	$162.95	$162.95	$162.90
Purchase #3	$124.29	7.490%	$133.5993	$133.60	$133.60	$133.60
Purchase #4	$163.66	5.314%	$172.3569	$172.36	$172.35	$172.40
Purchase #5	$168.54	13.617%	$191.4901	$191.49	$191.50	$191.50
Purchase #6	$134.37	7.783%	$144.828	$144.83	$144.85	$144.80
Purchase #7	$100.42	3.416%	$103.8503	$103.85	$103.85	$103.90
7 purchase totals =	$1,090.26		$1,165.0864	$1,165.09	$1,165.10	$1,165.10