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	$215.90	10.435%	$238.4292	$238.43	$238.45	$238.40
Purchase #2	$124.70	12.615%	$140.4309	$140.43	$140.45	$140.40
Purchase #3	$112.66	9.194%	$123.018	$123.02	$123.00	$123.00
Purchase #4	$226.78	11.587%	$253.057	$253.06	$253.05	$253.10
Purchase #5	$41.26	3.853%	$42.8497	$42.85	$42.85	$42.80
Purchase #6	$34.29	13.203%	$38.8173	$38.82	$38.80	$38.80
Purchase #7	$131.61	4.738%	$137.8457	$137.85	$137.85	$137.80
7 purchase totals =	$887.20		$974.4478	$974.46	$974.45	$974.30