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	$157.62	12.774%	$177.7544	$177.75	$177.75	$177.80
Purchase #2	$61.83	9.309%	$67.5858	$67.59	$67.60	$67.60
Purchase #3	$141.87	6.150%	$150.595	$150.60	$150.60	$150.60
Purchase #4	$246.98	10.315%	$272.456	$272.46	$272.45	$272.50
Purchase #5	$117.82	7.321%	$126.4456	$126.45	$126.45	$126.40
Purchase #6	$150.93	13.719%	$171.6361	$171.64	$171.65	$171.60
Purchase #7	$63.53	12.348%	$71.3747	$71.37	$71.35	$71.40
7 purchase totals =	$940.58		$1,037.8476	$1,037.86	$1,037.85	$1,037.90