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	$139.95	7.558%	$150.5274	$150.53	$150.55	$150.50
Purchase #2	$240.45	13.328%	$272.4972	$272.50	$272.50	$272.50
Purchase #3	$34.60	12.157%	$38.8063	$38.81	$38.80	$38.80
Purchase #4	$229.59	9.643%	$251.7294	$251.73	$251.75	$251.70
Purchase #5	$76.29	8.849%	$83.0409	$83.04	$83.05	$83.00
Purchase #6	$166.53	7.119%	$178.3853	$178.39	$178.40	$178.40
Purchase #7	$137.47	10.850%	$152.3855	$152.39	$152.40	$152.40
7 purchase totals =	$1,024.88		$1,127.3720	$1,127.39	$1,127.45	$1,127.30