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	$250.39	6.420%	$266.465	$266.47	$266.45	$266.50
Purchase #2	$81.60	11.636%	$91.095	$91.10	$91.10	$91.10
Purchase #3	$198.54	11.509%	$221.39	$221.39	$221.40	$221.40
Purchase #4	$214.46	11.186%	$238.4495	$238.45	$238.45	$238.40
Purchase #5	$38.25	13.841%	$43.5442	$43.54	$43.55	$43.50
Purchase #6	$94.60	6.105%	$100.3753	$100.38	$100.40	$100.40
Purchase #7	$213.91	11.199%	$237.8658	$237.87	$237.85	$237.90
7 purchase totals =	$1,091.75		$1,199.1848	$1,199.20	$1,199.20	$1,199.20