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	$39.95	9.713%	$43.8303	$43.83	$43.85	$43.80
Purchase #2	$141.55	3.234%	$146.1277	$146.13	$146.15	$146.10
Purchase #3	$143.62	8.732%	$156.1609	$156.16	$156.15	$156.20
Purchase #4	$58.99	9.568%	$64.6342	$64.63	$64.65	$64.60
Purchase #5	$190.51	12.377%	$214.0894	$214.09	$214.10	$214.10
Purchase #6	$183.68	6.846%	$196.2547	$196.25	$196.25	$196.30
Purchase #7	$129.39	6.242%	$137.4665	$137.47	$137.45	$137.50
7 purchase totals =	$887.69		$958.5637	$958.56	$958.60	$958.60