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	$114.49	10.806%	$126.8618	$126.86	$126.85	$126.90
Purchase #2	$33.31	9.256%	$36.3932	$36.39	$36.40	$36.40
Purchase #3	$34.32	8.623%	$37.2794	$37.28	$37.30	$37.30
Purchase #4	$153.30	3.161%	$158.1458	$158.15	$158.15	$158.10
Purchase #5	$115.67	6.830%	$123.5703	$123.57	$123.55	$123.60
Purchase #6	$196.76	12.507%	$221.3688	$221.37	$221.35	$221.40
Purchase #7	$199.89	4.462%	$208.8091	$208.81	$208.80	$208.80
7 purchase totals =	$847.74		$912.4284	$912.43	$912.40	$912.50