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	$144.25	6.595%	$153.7633	$153.76	$153.75	$153.80
Purchase #2	$222.76	8.423%	$241.5231	$241.52	$241.50	$241.50
Purchase #3	$162.85	5.604%	$171.9761	$171.98	$172.00	$172.00
Purchase #4	$6.34	13.475%	$7.1943	$7.19	$7.20	$7.20
Purchase #5	$196.91	10.289%	$217.1701	$217.17	$217.15	$217.20
Purchase #6	$37.38	9.289%	$40.8522	$40.85	$40.85	$40.90
Purchase #7	$148.78	13.316%	$168.5915	$168.59	$168.60	$168.60
7 purchase totals =	$919.27		$1,001.0706	$1,001.06	$1,001.05	$1,001.20