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	$40.53	11.365%	$45.1362	$45.14	$45.15	$45.10
Purchase #2	$158.30	7.128%	$169.5836	$169.58	$169.60	$169.60
Purchase #3	$95.86	9.520%	$104.9859	$104.99	$105.00	$105.00
Purchase #4	$99.80	13.845%	$113.6173	$113.62	$113.60	$113.60
Purchase #5	$237.46	10.703%	$262.8753	$262.88	$262.90	$262.90
Purchase #6	$13.65	4.802%	$14.3055	$14.31	$14.30	$14.30
Purchase #7	$215.42	4.669%	$225.478	$225.48	$225.50	$225.50
7 purchase totals =	$861.02		$935.9818	$936.00	$936.05	$936.00