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	$144.56	9.509%	$158.3062	$158.31	$158.30	$158.30
Purchase #2	$100.87	13.534%	$114.5217	$114.52	$114.50	$114.50
Purchase #3	$92.94	6.105%	$98.614	$98.61	$98.60	$98.60
Purchase #4	$226.62	13.617%	$257.4788	$257.48	$257.50	$257.50
Purchase #5	$192.99	10.641%	$213.5261	$213.53	$213.55	$213.50
Purchase #6	$190.55	4.667%	$199.443	$199.44	$199.45	$199.40
Purchase #7	$46.96	11.667%	$52.4388	$52.44	$52.45	$52.40
7 purchase totals =	$995.49		$1,094.3286	$1,094.33	$1,094.35	$1,094.20