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	$164.74	3.822%	$171.0364	$171.04	$171.05	$171.00
Purchase #2	$109.46	12.859%	$123.5355	$123.54	$123.55	$123.50
Purchase #3	$226.53	8.513%	$245.8145	$245.81	$245.80	$245.80
Purchase #4	$158.64	3.843%	$164.7365	$164.74	$164.75	$164.70
Purchase #5	$119.28	5.527%	$125.8726	$125.87	$125.85	$125.90
Purchase #6	$245.82	4.799%	$257.6169	$257.62	$257.60	$257.60
Purchase #7	$32.54	7.127%	$34.8591	$34.86	$34.85	$34.90
7 purchase totals =	$1,057.01		$1,123.4715	$1,123.48	$1,123.45	$1,123.40