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	$195.84	13.542%	$222.3607	$222.36	$222.35	$222.40
Purchase #2	$19.40	4.264%	$20.2272	$20.23	$20.25	$20.20
Purchase #3	$214.39	6.733%	$228.8249	$228.82	$228.80	$228.80
Purchase #4	$30.83	4.209%	$32.1276	$32.13	$32.15	$32.10
Purchase #5	$137.41	10.196%	$151.4203	$151.42	$151.40	$151.40
Purchase #6	$59.26	12.348%	$66.5774	$66.58	$66.60	$66.60
Purchase #7	$162.32	8.813%	$176.6253	$176.63	$176.65	$176.60
7 purchase totals =	$819.45		$898.1634	$898.17	$898.20	$898.10