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	$13.89	4.703%	$14.5432	$14.54	$14.55	$14.50
Purchase #2	$148.81	3.798%	$154.4618	$154.46	$154.45	$154.50
Purchase #3	$36.78	13.665%	$41.806	$41.81	$41.80	$41.80
Purchase #4	$34.75	12.565%	$39.1163	$39.12	$39.10	$39.10
Purchase #5	$107.43	13.207%	$121.6183	$121.62	$121.60	$121.60
Purchase #6	$82.49	3.624%	$85.4794	$85.48	$85.50	$85.50
Purchase #7	$105.38	7.686%	$113.4795	$113.48	$113.50	$113.50
7 purchase totals =	$529.53		$570.5045	$570.51	$570.50	$570.50