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	$162.52	3.555%	$168.2976	$168.30	$168.30	$168.30
Purchase #2	$183.76	8.581%	$199.5284	$199.53	$199.55	$199.50
Purchase #3	$150.71	12.328%	$169.2895	$169.29	$169.30	$169.30
Purchase #4	$99.73	7.812%	$107.5209	$107.52	$107.50	$107.50
Purchase #5	$63.58	10.481%	$70.2438	$70.24	$70.25	$70.20
Purchase #6	$99.90	3.359%	$103.2556	$103.26	$103.25	$103.30
Purchase #7	$204.83	5.182%	$215.4443	$215.44	$215.45	$215.40
7 purchase totals =	$965.03		$1,033.5801	$1,033.58	$1,033.60	$1,033.50