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	$63.45	11.770%	$70.9181	$70.92	$70.90	$70.90
Purchase #2	$53.95	12.160%	$60.5103	$60.51	$60.50	$60.50
Purchase #3	$198.43	12.241%	$222.7198	$222.72	$222.70	$222.70
Purchase #4	$179.59	9.801%	$197.1916	$197.19	$197.20	$197.20
Purchase #5	$162.72	3.803%	$168.9082	$168.91	$168.90	$168.90
Purchase #6	$101.86	3.802%	$105.7327	$105.73	$105.75	$105.70
Purchase #7	$129.93	10.660%	$143.7805	$143.78	$143.80	$143.80
7 purchase totals =	$889.93		$969.7612	$969.76	$969.75	$969.70