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	$101.31	3.234%	$104.5864	$104.59	$104.60	$104.60
Purchase #2	$198.50	7.556%	$213.4987	$213.50	$213.50	$213.50
Purchase #3	$230.86	3.750%	$239.5173	$239.52	$239.50	$239.50
Purchase #4	$114.45	13.866%	$130.3196	$130.32	$130.30	$130.30
Purchase #5	$190.35	8.538%	$206.6021	$206.60	$206.60	$206.60
Purchase #6	$105.72	10.105%	$116.403	$116.40	$116.40	$116.40
Purchase #7	$29.87	3.645%	$30.9588	$30.96	$30.95	$31.00
7 purchase totals =	$971.06		$1,041.8859	$1,041.89	$1,041.85	$1,041.90