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	$206.56	7.605%	$222.2689	$222.27	$222.25	$222.30
Purchase #2	$109.37	7.354%	$117.4131	$117.41	$117.40	$117.40
Purchase #3	$116.69	12.758%	$131.5773	$131.58	$131.60	$131.60
Purchase #4	$226.49	11.503%	$252.5431	$252.54	$252.55	$252.50
Purchase #5	$239.71	12.742%	$270.2538	$270.25	$270.25	$270.30
Purchase #6	$21.45	12.285%	$24.0851	$24.09	$24.10	$24.10
Purchase #7	$39.61	8.301%	$42.898	$42.90	$42.90	$42.90
7 purchase totals =	$959.88		$1,061.0393	$1,061.04	$1,061.05	$1,061.10