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	$86.54	10.773%	$95.863	$95.86	$95.85	$95.90
Purchase #2	$29.39	10.503%	$32.4768	$32.48	$32.50	$32.50
Purchase #3	$214.57	11.212%	$238.6276	$238.63	$238.65	$238.60
Purchase #4	$216.52	8.253%	$234.3894	$234.39	$234.40	$234.40
Purchase #5	$32.78	11.693%	$36.613	$36.61	$36.60	$36.60
Purchase #6	$242.56	7.366%	$260.427	$260.43	$260.45	$260.40
Purchase #7	$18.78	4.622%	$19.648	$19.65	$19.65	$19.60
7 purchase totals =	$841.14		$918.0448	$918.05	$918.10	$918.00