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	$119.85	9.663%	$131.4311	$131.43	$131.45	$131.40
Purchase #2	$101.52	12.820%	$114.5349	$114.53	$114.55	$114.50
Purchase #3	$127.72	12.238%	$143.3504	$143.35	$143.35	$143.40
Purchase #4	$218.55	12.847%	$246.6271	$246.63	$246.65	$246.60
Purchase #5	$177.84	11.614%	$198.4943	$198.49	$198.50	$198.50
Purchase #6	$113.70	8.612%	$123.4918	$123.49	$123.50	$123.50
Purchase #7	$72.85	6.786%	$77.7936	$77.79	$77.80	$77.80
7 purchase totals =	$932.03		$1,035.7232	$1,035.71	$1,035.80	$1,035.70