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	$246.27	4.532%	$257.431	$257.43	$257.45	$257.40
Purchase #2	$143.93	12.142%	$161.406	$161.41	$161.40	$161.40
Purchase #3	$49.53	5.788%	$52.3968	$52.40	$52.40	$52.40
Purchase #4	$8.61	13.632%	$9.7837	$9.78	$9.80	$9.80
Purchase #5	$86.37	3.584%	$89.4655	$89.47	$89.45	$89.50
Purchase #6	$132.83	3.845%	$137.9373	$137.94	$137.95	$137.90
Purchase #7	$149.29	4.753%	$156.3858	$156.39	$156.40	$156.40
7 purchase totals =	$816.83		$864.8061	$864.82	$864.85	$864.80