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	$32.48	6.417%	$34.5642	$34.56	$34.55	$34.60
Purchase #2	$31.97	12.755%	$36.0478	$36.05	$36.05	$36.00
Purchase #3	$153.48	12.627%	$172.8599	$172.86	$172.85	$172.90
Purchase #4	$104.67	12.738%	$118.0029	$118.00	$118.00	$118.00
Purchase #5	$60.40	7.371%	$64.8521	$64.85	$64.85	$64.90
Purchase #6	$60.61	7.423%	$65.1091	$65.11	$65.10	$65.10
Purchase #7	$84.32	7.291%	$90.4678	$90.47	$90.45	$90.50
7 purchase totals =	$527.93		$581.9038	$581.90	$581.85	$582.00