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	$248.63	12.863%	$280.6113	$280.61	$280.60	$280.60
Purchase #2	$23.50	12.384%	$26.4102	$26.41	$26.40	$26.40
Purchase #3	$212.70	13.467%	$241.3443	$241.34	$241.35	$241.30
Purchase #4	$97.87	5.664%	$103.4134	$103.41	$103.40	$103.40
Purchase #5	$208.74	7.135%	$223.6336	$223.63	$223.65	$223.60
Purchase #6	$212.68	4.762%	$222.8078	$222.81	$222.80	$222.80
Purchase #7	$73.27	12.501%	$82.4295	$82.43	$82.45	$82.40
7 purchase totals =	$1,077.39		$1,180.6501	$1,180.64	$1,180.65	$1,180.50