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	$48.80	11.825%	$54.5706	$54.57	$54.55	$54.60
Purchase #2	$58.26	12.312%	$65.433	$65.43	$65.45	$65.40
Purchase #3	$31.26	11.577%	$34.879	$34.88	$34.90	$34.90
Purchase #4	$10.83	6.514%	$11.5355	$11.54	$11.55	$11.50
Purchase #5	$143.46	11.727%	$160.2836	$160.28	$160.30	$160.30
Purchase #6	$37.54	5.569%	$39.6306	$39.63	$39.65	$39.60
Purchase #7	$70.93	10.719%	$78.533	$78.53	$78.55	$78.50
7 purchase totals =	$401.08		$444.8653	$444.86	$444.95	$444.80