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	$179.25	3.587%	$185.6797	$185.68	$185.70	$185.70
Purchase #2	$144.59	7.163%	$154.947	$154.95	$154.95	$154.90
Purchase #3	$192.93	3.431%	$199.5494	$199.55	$199.55	$199.50
Purchase #4	$86.45	13.477%	$98.1009	$98.10	$98.10	$98.10
Purchase #5	$228.83	11.704%	$255.6123	$255.61	$255.60	$255.60
Purchase #6	$121.63	12.590%	$136.9432	$136.94	$136.95	$136.90
Purchase #7	$242.89	5.763%	$256.8878	$256.89	$256.90	$256.90
7 purchase totals =	$1,196.57		$1,287.7203	$1,287.72	$1,287.75	$1,287.60