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	$110.79	5.469%	$116.8491	$116.85	$116.85	$116.80
Purchase #2	$48.52	7.127%	$51.978	$51.98	$52.00	$52.00
Purchase #3	$50.47	12.683%	$56.8711	$56.87	$56.85	$56.90
Purchase #4	$56.68	4.456%	$59.2057	$59.21	$59.20	$59.20
Purchase #5	$20.96	4.675%	$21.9399	$21.94	$21.95	$21.90
Purchase #6	$82.60	4.728%	$86.5053	$86.51	$86.50	$86.50
Purchase #7	$16.76	5.441%	$17.6719	$17.67	$17.65	$17.70
7 purchase totals =	$386.78		$411.0210	$411.03	$411.00	$411.00