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	$72.94	7.347%	$78.2989	$78.30	$78.30	$78.30
Purchase #2	$192.46	11.178%	$213.9732	$213.97	$213.95	$214.00
Purchase #3	$15.40	3.333%	$15.9133	$15.91	$15.90	$15.90
Purchase #4	$87.40	11.661%	$97.5917	$97.59	$97.60	$97.60
Purchase #5	$75.95	3.835%	$78.8627	$78.86	$78.85	$78.90
Purchase #6	$12.48	7.845%	$13.4591	$13.46	$13.45	$13.50
Purchase #7	$228.40	12.284%	$256.4567	$256.46	$256.45	$256.50
7 purchase totals =	$685.03		$754.5556	$754.55	$754.50	$754.70