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	$156.48	8.850%	$170.3285	$170.33	$170.35	$170.30
Purchase #2	$26.32	5.236%	$27.6981	$27.70	$27.70	$27.70
Purchase #3	$111.81	10.687%	$123.7591	$123.76	$123.75	$123.80
Purchase #4	$38.99	4.589%	$40.7793	$40.78	$40.80	$40.80
Purchase #5	$222.33	8.636%	$241.5304	$241.53	$241.55	$241.50
Purchase #6	$232.53	10.365%	$256.6317	$256.63	$256.65	$256.60
Purchase #7	$240.30	12.720%	$270.8662	$270.87	$270.85	$270.90
7 purchase totals =	$1,028.76		$1,131.5933	$1,131.60	$1,131.65	$1,131.60