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	$54.33	11.811%	$60.7469	$60.75	$60.75	$60.70
Purchase #2	$237.57	3.506%	$245.8992	$245.90	$245.90	$245.90
Purchase #3	$236.89	3.457%	$245.0793	$245.08	$245.10	$245.10
Purchase #4	$63.61	12.296%	$71.4315	$71.43	$71.45	$71.40
Purchase #5	$137.34	3.590%	$142.2705	$142.27	$142.25	$142.30
Purchase #6	$183.70	9.330%	$200.8392	$200.84	$200.85	$200.80
Purchase #7	$123.63	7.517%	$132.9233	$132.92	$132.90	$132.90
7 purchase totals =	$1,037.07		$1,099.1899	$1,099.19	$1,099.20	$1,099.10