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	$233.73	9.792%	$256.6168	$256.62	$256.60	$256.60
Purchase #2	$38.72	13.373%	$43.898	$43.90	$43.90	$43.90
Purchase #3	$96.66	8.497%	$104.8732	$104.87	$104.85	$104.90
Purchase #4	$24.38	13.150%	$27.586	$27.59	$27.60	$27.60
Purchase #5	$39.43	12.819%	$44.4845	$44.48	$44.50	$44.50
Purchase #6	$98.60	3.401%	$101.9534	$101.95	$101.95	$102.00
Purchase #7	$109.83	3.782%	$113.9838	$113.98	$114.00	$114.00
7 purchase totals =	$641.35		$693.3957	$693.39	$693.40	$693.50