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	$177.49	8.532%	$192.6334	$192.63	$192.65	$192.60
Purchase #2	$123.35	6.845%	$131.7933	$131.79	$131.80	$131.80
Purchase #3	$77.59	6.239%	$82.4308	$82.43	$82.45	$82.40
Purchase #4	$181.37	10.541%	$200.4882	$200.49	$200.50	$200.50
Purchase #5	$250.41	12.732%	$282.2922	$282.29	$282.30	$282.30
Purchase #6	$126.95	13.532%	$144.1289	$144.13	$144.15	$144.10
Purchase #7	$108.30	11.520%	$120.7762	$120.78	$120.80	$120.80
7 purchase totals =	$1,045.46		$1,154.5430	$1,154.54	$1,154.65	$1,154.50