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	$121.48	5.116%	$127.6949	$127.69	$127.70	$127.70
Purchase #2	$220.95	3.426%	$228.5197	$228.52	$228.50	$228.50
Purchase #3	$187.83	6.615%	$200.255	$200.26	$200.25	$200.30
Purchase #4	$139.45	3.534%	$144.3782	$144.38	$144.40	$144.40
Purchase #5	$22.45	10.866%	$24.8894	$24.89	$24.90	$24.90
Purchase #6	$180.59	8.732%	$196.3591	$196.36	$196.35	$196.40
Purchase #7	$8.27	6.868%	$8.838	$8.84	$8.85	$8.80
7 purchase totals =	$881.02		$930.9343	$930.94	$930.95	$931.00