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	$78.50	8.826%	$85.4284	$85.43	$85.45	$85.40
Purchase #2	$241.77	13.115%	$273.4781	$273.48	$273.50	$273.50
Purchase #3	$43.67	3.311%	$45.1159	$45.12	$45.10	$45.10
Purchase #4	$96.76	7.460%	$103.9783	$103.98	$104.00	$104.00
Purchase #5	$241.97	13.814%	$275.3957	$275.40	$275.40	$275.40
Purchase #6	$117.57	12.602%	$132.3862	$132.39	$132.40	$132.40
Purchase #7	$131.60	9.150%	$143.6414	$143.64	$143.65	$143.60
7 purchase totals =	$951.84		$1,059.4240	$1,059.44	$1,059.50	$1,059.40