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	$200.63	7.636%	$215.9501	$215.95	$215.95	$216.00
Purchase #2	$137.40	12.371%	$154.3978	$154.40	$154.40	$154.40
Purchase #3	$28.43	7.426%	$30.5412	$30.54	$30.55	$30.50
Purchase #4	$36.87	5.368%	$38.8492	$38.85	$38.85	$38.80
Purchase #5	$129.46	11.389%	$144.2042	$144.20	$144.20	$144.20
Purchase #6	$123.42	6.873%	$131.9027	$131.90	$131.90	$131.90
Purchase #7	$190.51	3.225%	$196.6539	$196.65	$196.65	$196.70
7 purchase totals =	$846.72		$912.4991	$912.49	$912.50	$912.50