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	$81.72	4.536%	$85.4268	$85.43	$85.45	$85.40
Purchase #2	$127.85	8.774%	$139.0676	$139.07	$139.05	$139.10
Purchase #3	$49.93	3.207%	$51.5313	$51.53	$51.55	$51.50
Purchase #4	$11.26	5.543%	$11.8841	$11.88	$11.90	$11.90
Purchase #5	$59.71	3.660%	$61.8954	$61.90	$61.90	$61.90
Purchase #6	$90.42	8.801%	$98.3779	$98.38	$98.40	$98.40
Purchase #7	$144.80	9.507%	$158.5661	$158.57	$158.55	$158.60
7 purchase totals =	$565.69		$606.7492	$606.76	$606.80	$606.80