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	$30.29	11.689%	$33.8306	$33.83	$33.85	$33.80
Purchase #2	$18.98	13.758%	$21.5913	$21.59	$21.60	$21.60
Purchase #3	$195.81	11.317%	$217.9698	$217.97	$217.95	$218.00
Purchase #4	$34.41	9.325%	$37.6187	$37.62	$37.60	$37.60
Purchase #5	$130.83	5.115%	$137.522	$137.52	$137.50	$137.50
Purchase #6	$40.36	4.378%	$42.127	$42.13	$42.15	$42.10
Purchase #7	$205.65	11.275%	$228.837	$228.84	$228.85	$228.80
7 purchase totals =	$656.33		$719.4964	$719.50	$719.50	$719.40