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	$248.77	13.615%	$282.64	$282.64	$282.65	$282.60
Purchase #2	$233.95	11.410%	$260.6437	$260.64	$260.65	$260.60
Purchase #3	$138.44	13.359%	$156.9342	$156.93	$156.95	$156.90
Purchase #4	$104.32	13.146%	$118.0339	$118.03	$118.05	$118.00
Purchase #5	$162.82	5.401%	$171.6139	$171.61	$171.60	$171.60
Purchase #6	$136.25	11.869%	$152.4215	$152.42	$152.40	$152.40
Purchase #7	$219.86	10.421%	$242.7716	$242.77	$242.75	$242.80
7 purchase totals =	$1,244.41		$1,385.0588	$1,385.04	$1,385.05	$1,384.90