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	$228.58	9.839%	$251.07	$251.07	$251.05	$251.10
Purchase #2	$165.40	10.109%	$182.1203	$182.12	$182.10	$182.10
Purchase #3	$119.47	10.304%	$131.7802	$131.78	$131.80	$131.80
Purchase #4	$117.63	12.269%	$132.062	$132.06	$132.05	$132.10
Purchase #5	$217.99	6.357%	$231.8476	$231.85	$231.85	$231.80
Purchase #6	$175.94	11.600%	$196.349	$196.35	$196.35	$196.30
Purchase #7	$51.75	6.766%	$55.2514	$55.25	$55.25	$55.30
7 purchase totals =	$1,076.76		$1,180.4805	$1,180.48	$1,180.45	$1,180.50