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	$77.56	11.742%	$86.6671	$86.67	$86.65	$86.70
Purchase #2	$116.94	12.800%	$131.9083	$131.91	$131.90	$131.90
Purchase #3	$177.96	7.492%	$191.2928	$191.29	$191.30	$191.30
Purchase #4	$167.53	10.866%	$185.7338	$185.73	$185.75	$185.70
Purchase #5	$117.65	8.453%	$127.595	$127.60	$127.60	$127.60
Purchase #6	$80.37	4.202%	$83.7471	$83.75	$83.75	$83.70
Purchase #7	$201.65	10.138%	$222.0933	$222.09	$222.10	$222.10
7 purchase totals =	$939.66		$1,029.0374	$1,029.04	$1,029.05	$1,029.00