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	$111.87	9.494%	$122.4909	$122.49	$122.50	$122.50
Purchase #2	$126.52	11.327%	$140.8509	$140.85	$140.85	$140.90
Purchase #3	$139.86	6.431%	$148.8544	$148.85	$148.85	$148.90
Purchase #4	$119.83	12.269%	$134.5319	$134.53	$134.55	$134.50
Purchase #5	$110.82	11.859%	$123.9621	$123.96	$123.95	$124.00
Purchase #6	$144.33	6.630%	$153.8991	$153.90	$153.90	$153.90
Purchase #7	$160.29	11.179%	$178.2088	$178.21	$178.20	$178.20
7 purchase totals =	$913.52		$1,002.7981	$1,002.79	$1,002.80	$1,002.90