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	$82.53	5.394%	$86.9817	$86.98	$87.00	$87.00
Purchase #2	$216.53	3.210%	$223.4806	$223.48	$223.50	$223.50
Purchase #3	$13.87	12.426%	$15.5935	$15.59	$15.60	$15.60
Purchase #4	$118.36	3.177%	$122.1203	$122.12	$122.10	$122.10
Purchase #5	$95.52	8.817%	$103.942	$103.94	$103.95	$103.90
Purchase #6	$226.57	10.751%	$250.9285	$250.93	$250.95	$250.90
Purchase #7	$74.71	5.538%	$78.8474	$78.85	$78.85	$78.80
7 purchase totals =	$828.09		$881.8940	$881.89	$881.95	$881.80