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	$89.33	7.193%	$95.7555	$95.76	$95.75	$95.80
Purchase #2	$233.71	5.614%	$246.8305	$246.83	$246.85	$246.80
Purchase #3	$71.83	12.257%	$80.6342	$80.63	$80.65	$80.60
Purchase #4	$162.28	9.247%	$177.286	$177.29	$177.30	$177.30
Purchase #5	$71.89	6.381%	$76.4773	$76.48	$76.50	$76.50
Purchase #6	$78.60	5.382%	$82.8303	$82.83	$82.85	$82.80
Purchase #7	$48.68	7.693%	$52.425	$52.43	$52.45	$52.40
7 purchase totals =	$756.32		$812.2388	$812.25	$812.35	$812.20