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	$61.98	12.193%	$69.5372	$69.54	$69.55	$69.50
Purchase #2	$12.50	11.549%	$13.9436	$13.94	$13.95	$13.90
Purchase #3	$171.77	6.624%	$183.148	$183.15	$183.15	$183.10
Purchase #4	$55.55	13.399%	$62.9931	$62.99	$63.00	$63.00
Purchase #5	$11.32	10.601%	$12.52	$12.52	$12.50	$12.50
Purchase #6	$117.52	8.638%	$127.6714	$127.67	$127.65	$127.70
Purchase #7	$163.50	9.553%	$179.1192	$179.12	$179.10	$179.10
7 purchase totals =	$594.14		$648.9325	$648.93	$648.90	$648.80