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	$133.77	7.408%	$143.6797	$143.68	$143.70	$143.70
Purchase #2	$84.46	5.831%	$89.3849	$89.38	$89.40	$89.40
Purchase #3	$42.91	6.258%	$45.5953	$45.60	$45.60	$45.60
Purchase #4	$158.62	8.621%	$172.2946	$172.29	$172.30	$172.30
Purchase #5	$13.92	3.813%	$14.4508	$14.45	$14.45	$14.50
Purchase #6	$233.85	6.792%	$249.7331	$249.73	$249.75	$249.70
Purchase #7	$139.51	8.163%	$150.8982	$150.90	$150.90	$150.90
7 purchase totals =	$807.04		$866.0366	$866.03	$866.10	$866.10