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	$39.72	4.215%	$41.3942	$41.39	$41.40	$41.40
Purchase #2	$43.32	7.550%	$46.5907	$46.59	$46.60	$46.60
Purchase #3	$196.87	8.135%	$212.8854	$212.89	$212.90	$212.90
Purchase #4	$64.30	11.238%	$71.526	$71.53	$71.55	$71.50
Purchase #5	$166.61	3.805%	$172.9495	$172.95	$172.95	$172.90
Purchase #6	$83.71	4.524%	$87.497	$87.50	$87.50	$87.50
Purchase #7	$75.51	12.686%	$85.0892	$85.09	$85.10	$85.10
7 purchase totals =	$670.04		$717.9320	$717.94	$718.00	$717.90