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	$62.84	8.739%	$68.3316	$68.33	$68.35	$68.30
Purchase #2	$138.64	6.691%	$147.9164	$147.92	$147.90	$147.90
Purchase #3	$40.98	11.382%	$45.6443	$45.64	$45.65	$45.60
Purchase #4	$94.41	12.115%	$105.8478	$105.85	$105.85	$105.80
Purchase #5	$92.32	13.823%	$105.0814	$105.08	$105.10	$105.10
Purchase #6	$171.60	12.171%	$192.4854	$192.49	$192.50	$192.50
Purchase #7	$200.78	10.729%	$222.3217	$222.32	$222.30	$222.30
7 purchase totals =	$801.57		$887.6286	$887.63	$887.65	$887.50