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	$85.61	12.475%	$96.2898	$96.29	$96.30	$96.30
Purchase #2	$133.65	9.579%	$146.4523	$146.45	$146.45	$146.50
Purchase #3	$31.75	9.413%	$34.7386	$34.74	$34.75	$34.70
Purchase #4	$157.91	4.168%	$164.4917	$164.49	$164.50	$164.50
Purchase #5	$241.55	8.665%	$262.4803	$262.48	$262.50	$262.50
Purchase #6	$94.61	11.172%	$105.1798	$105.18	$105.20	$105.20
Purchase #7	$48.88	7.545%	$52.568	$52.57	$52.55	$52.60
7 purchase totals =	$793.96		$862.2005	$862.20	$862.25	$862.30