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	$185.34	12.243%	$208.0312	$208.03	$208.05	$208.00
Purchase #2	$135.45	12.601%	$152.5181	$152.52	$152.50	$152.50
Purchase #3	$47.27	7.529%	$50.829	$50.83	$50.85	$50.80
Purchase #4	$56.42	12.604%	$63.5312	$63.53	$63.55	$63.50
Purchase #5	$57.81	3.702%	$59.9501	$59.95	$59.95	$60.00
Purchase #6	$35.71	13.184%	$40.418	$40.42	$40.40	$40.40
Purchase #7	$20.87	12.530%	$23.485	$23.49	$23.50	$23.50
7 purchase totals =	$538.87		$598.7626	$598.77	$598.80	$598.70