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	$29.80	11.337%	$33.1784	$33.18	$33.20	$33.20
Purchase #2	$40.88	7.196%	$43.8217	$43.82	$43.80	$43.80
Purchase #3	$18.87	13.508%	$21.419	$21.42	$21.40	$21.40
Purchase #4	$64.98	11.249%	$72.2896	$72.29	$72.30	$72.30
Purchase #5	$38.58	4.740%	$40.4087	$40.41	$40.40	$40.40
Purchase #6	$108.57	5.378%	$114.4089	$114.41	$114.40	$114.40
Purchase #7	$24.85	9.715%	$27.2642	$27.26	$27.25	$27.30
7 purchase totals =	$326.53		$352.7905	$352.79	$352.75	$352.80