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	$155.94	13.561%	$177.087	$177.09	$177.10	$177.10
Purchase #2	$58.27	8.658%	$63.315	$63.32	$63.30	$63.30
Purchase #3	$138.39	11.345%	$154.0903	$154.09	$154.10	$154.10
Purchase #4	$93.66	7.820%	$100.9842	$100.98	$101.00	$101.00
Purchase #5	$171.32	11.178%	$190.4701	$190.47	$190.45	$190.50
Purchase #6	$196.39	12.855%	$221.6359	$221.64	$221.65	$221.60
Purchase #7	$72.80	13.870%	$82.8974	$82.90	$82.90	$82.90
7 purchase totals =	$886.77		$990.4799	$990.49	$990.50	$990.50