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	$196.85	9.648%	$215.8421	$215.84	$215.85	$215.80
Purchase #2	$139.51	8.619%	$151.5344	$151.53	$151.55	$151.50
Purchase #3	$63.94	13.221%	$72.3935	$72.39	$72.40	$72.40
Purchase #4	$212.88	11.147%	$236.6097	$236.61	$236.60	$236.60
Purchase #5	$85.75	4.393%	$89.517	$89.52	$89.50	$89.50
Purchase #6	$14.62	5.224%	$15.3837	$15.38	$15.40	$15.40
Purchase #7	$121.99	13.704%	$138.7075	$138.71	$138.70	$138.70
7 purchase totals =	$835.54		$919.9879	$919.98	$920.00	$919.90