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	$82.59	10.350%	$91.1381	$91.14	$91.15	$91.10
Purchase #2	$198.28	12.395%	$222.8568	$222.86	$222.85	$222.90
Purchase #3	$217.94	4.224%	$227.1458	$227.15	$227.15	$227.10
Purchase #4	$234.61	13.243%	$265.6794	$265.68	$265.70	$265.70
Purchase #5	$13.96	10.227%	$15.3877	$15.39	$15.40	$15.40
Purchase #6	$200.27	6.665%	$213.618	$213.62	$213.60	$213.60
Purchase #7	$62.45	4.324%	$65.1503	$65.15	$65.15	$65.20
7 purchase totals =	$1,010.10		$1,100.9761	$1,100.99	$1,101.00	$1,101.00