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	$168.66	8.167%	$182.4345	$182.43	$182.45	$182.40
Purchase #2	$133.59	7.869%	$144.1022	$144.10	$144.10	$144.10
Purchase #3	$128.85	8.206%	$139.4234	$139.42	$139.40	$139.40
Purchase #4	$60.57	4.767%	$63.4574	$63.46	$63.45	$63.50
Purchase #5	$19.59	11.856%	$21.9126	$21.91	$21.90	$21.90
Purchase #6	$150.28	11.856%	$168.0972	$168.10	$168.10	$168.10
Purchase #7	$109.85	11.439%	$122.4157	$122.42	$122.40	$122.40
7 purchase totals =	$771.39		$841.8430	$841.84	$841.80	$841.80