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	$36.66	13.595%	$41.6439	$41.64	$41.65	$41.60
Purchase #2	$239.96	3.680%	$248.7905	$248.79	$248.80	$248.80
Purchase #3	$11.31	11.549%	$12.6162	$12.62	$12.60	$12.60
Purchase #4	$98.30	7.139%	$105.3176	$105.32	$105.30	$105.30
Purchase #5	$14.76	5.325%	$15.546	$15.55	$15.55	$15.50
Purchase #6	$178.58	6.738%	$190.6127	$190.61	$190.60	$190.60
Purchase #7	$19.99	5.792%	$21.1478	$21.15	$21.15	$21.10
7 purchase totals =	$599.56		$635.6747	$635.68	$635.65	$635.50