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	$93.27	13.224%	$105.604	$105.60	$105.60	$105.60
Purchase #2	$125.31	7.619%	$134.8574	$134.86	$134.85	$134.90
Purchase #3	$231.58	10.224%	$255.2567	$255.26	$255.25	$255.30
Purchase #4	$102.34	9.296%	$111.8535	$111.85	$111.85	$111.90
Purchase #5	$200.87	12.667%	$226.3142	$226.31	$226.30	$226.30
Purchase #6	$49.51	4.691%	$51.8325	$51.83	$51.85	$51.80
Purchase #7	$219.47	8.446%	$238.0064	$238.01	$238.00	$238.00
7 purchase totals =	$1,022.35		$1,123.7247	$1,123.72	$1,123.70	$1,123.80