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	$86.45	12.718%	$97.4447	$97.44	$97.45	$97.40
Purchase #2	$106.96	5.497%	$112.8396	$112.84	$112.85	$112.80
Purchase #3	$34.39	12.206%	$38.5876	$38.59	$38.60	$38.60
Purchase #4	$121.46	7.158%	$130.1541	$130.15	$130.15	$130.20
Purchase #5	$228.79	11.705%	$255.5699	$255.57	$255.55	$255.60
Purchase #6	$206.43	4.405%	$215.5232	$215.52	$215.50	$215.50
Purchase #7	$72.53	13.657%	$82.4354	$82.44	$82.45	$82.40
7 purchase totals =	$857.01		$932.5545	$932.55	$932.55	$932.50