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	$153.74	5.393%	$162.0312	$162.03	$162.05	$162.00
Purchase #2	$61.44	7.327%	$65.9417	$65.94	$65.95	$65.90
Purchase #3	$85.53	6.184%	$90.8192	$90.82	$90.80	$90.80
Purchase #4	$241.59	6.763%	$257.9287	$257.93	$257.95	$257.90
Purchase #5	$80.52	12.774%	$90.8056	$90.81	$90.80	$90.80
Purchase #6	$161.70	5.176%	$170.0696	$170.07	$170.05	$170.10
Purchase #7	$111.92	6.564%	$119.2664	$119.27	$119.25	$119.30
7 purchase totals =	$896.44		$956.8624	$956.87	$956.85	$956.80