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	$225.49	7.297%	$241.944	$241.94	$241.95	$241.90
Purchase #2	$15.25	3.772%	$15.8252	$15.83	$15.85	$15.80
Purchase #3	$164.58	13.609%	$186.9777	$186.98	$187.00	$187.00
Purchase #4	$34.47	10.705%	$38.16	$38.16	$38.15	$38.20
Purchase #5	$182.52	4.564%	$190.8502	$190.85	$190.85	$190.90
Purchase #6	$41.73	9.636%	$45.7511	$45.75	$45.75	$45.80
Purchase #7	$199.90	8.751%	$217.3932	$217.39	$217.40	$217.40
7 purchase totals =	$863.94		$936.9014	$936.90	$936.95	$937.00