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	$116.44	10.660%	$128.8525	$128.85	$128.85	$128.90
Purchase #2	$239.75	12.378%	$269.4263	$269.43	$269.45	$269.40
Purchase #3	$139.52	11.182%	$155.1211	$155.12	$155.10	$155.10
Purchase #4	$37.32	12.441%	$41.963	$41.96	$41.95	$42.00
Purchase #5	$95.44	4.595%	$99.8255	$99.83	$99.85	$99.80
Purchase #6	$119.45	10.414%	$131.8895	$131.89	$131.90	$131.90
Purchase #7	$197.96	3.853%	$205.5874	$205.59	$205.60	$205.60
7 purchase totals =	$945.88		$1,032.6653	$1,032.67	$1,032.70	$1,032.70