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	$43.43	9.492%	$47.5524	$47.55	$47.55	$47.60
Purchase #2	$123.49	6.480%	$131.4922	$131.49	$131.50	$131.50
Purchase #3	$123.62	13.308%	$140.0713	$140.07	$140.05	$140.10
Purchase #4	$167.32	10.483%	$184.8602	$184.86	$184.85	$184.90
Purchase #5	$29.38	8.288%	$31.815	$31.82	$31.80	$31.80
Purchase #6	$156.53	7.720%	$168.6141	$168.61	$168.60	$168.60
Purchase #7	$240.28	8.642%	$261.045	$261.05	$261.05	$261.00
7 purchase totals =	$884.05		$965.4502	$965.45	$965.40	$965.50