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	$51.41	8.725%	$55.8955	$55.90	$55.90	$55.90
Purchase #2	$248.58	12.822%	$280.4529	$280.45	$280.45	$280.50
Purchase #3	$30.91	5.571%	$32.632	$32.63	$32.65	$32.60
Purchase #4	$221.87	5.339%	$233.7156	$233.72	$233.70	$233.70
Purchase #5	$230.55	3.451%	$238.5063	$238.51	$238.50	$238.50
Purchase #6	$59.40	7.575%	$63.8996	$63.90	$63.90	$63.90
Purchase #7	$175.29	13.767%	$199.4222	$199.42	$199.40	$199.40
7 purchase totals =	$1,018.01		$1,104.5241	$1,104.53	$1,104.50	$1,104.50