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	$58.49	10.492%	$64.6268	$64.63	$64.65	$64.60
Purchase #2	$180.84	11.704%	$202.0055	$202.01	$202.00	$202.00
Purchase #3	$82.42	3.505%	$85.3088	$85.31	$85.30	$85.30
Purchase #4	$111.75	10.712%	$123.7207	$123.72	$123.70	$123.70
Purchase #5	$78.98	8.246%	$85.4927	$85.49	$85.50	$85.50
Purchase #6	$14.82	3.473%	$15.3347	$15.33	$15.35	$15.30
Purchase #7	$37.74	8.224%	$40.8437	$40.84	$40.85	$40.80
7 purchase totals =	$565.04		$617.3329	$617.33	$617.35	$617.20