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	$117.75	5.241%	$123.9213	$123.92	$123.90	$123.90
Purchase #2	$86.36	13.232%	$97.7872	$97.79	$97.80	$97.80
Purchase #3	$78.72	4.678%	$82.4025	$82.40	$82.40	$82.40
Purchase #4	$102.81	8.873%	$111.9323	$111.93	$111.95	$111.90
Purchase #5	$60.94	11.782%	$68.12	$68.12	$68.10	$68.10
Purchase #6	$63.45	4.477%	$66.2907	$66.29	$66.30	$66.30
Purchase #7	$160.41	5.123%	$168.6278	$168.63	$168.65	$168.60
7 purchase totals =	$670.44		$719.0818	$719.08	$719.10	$719.00