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	$142.67	11.193%	$158.6391	$158.64	$158.65	$158.60
Purchase #2	$148.59	9.509%	$162.7194	$162.72	$162.70	$162.70
Purchase #3	$117.81	12.559%	$132.6058	$132.61	$132.60	$132.60
Purchase #4	$103.85	12.539%	$116.8718	$116.87	$116.85	$116.90
Purchase #5	$37.92	12.153%	$42.5284	$42.53	$42.55	$42.50
Purchase #6	$83.86	6.248%	$89.0996	$89.10	$89.10	$89.10
Purchase #7	$52.66	10.363%	$58.1172	$58.12	$58.10	$58.10
7 purchase totals =	$687.36		$760.5813	$760.59	$760.55	$760.50