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	$223.45	6.598%	$238.1932	$238.19	$238.20	$238.20
Purchase #2	$69.29	5.580%	$73.1564	$73.16	$73.15	$73.20
Purchase #3	$224.85	6.676%	$239.861	$239.86	$239.85	$239.90
Purchase #4	$96.97	8.609%	$105.3181	$105.32	$105.30	$105.30
Purchase #5	$100.67	4.750%	$105.4518	$105.45	$105.45	$105.50
Purchase #6	$24.43	10.805%	$27.0697	$27.07	$27.05	$27.10
Purchase #7	$138.42	4.119%	$144.1215	$144.12	$144.10	$144.10
7 purchase totals =	$878.08		$933.1717	$933.17	$933.10	$933.30