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	$102.40	13.797%	$116.5281	$116.53	$116.55	$116.50
Purchase #2	$65.88	8.800%	$71.6774	$71.68	$71.70	$71.70
Purchase #3	$178.57	9.466%	$195.4734	$195.47	$195.45	$195.50
Purchase #4	$100.93	13.805%	$114.8634	$114.86	$114.85	$114.90
Purchase #5	$134.78	5.719%	$142.4881	$142.49	$142.50	$142.50
Purchase #6	$146.99	10.523%	$162.4578	$162.46	$162.45	$162.50
Purchase #7	$76.75	7.638%	$82.6122	$82.61	$82.60	$82.60
7 purchase totals =	$806.30		$886.1004	$886.10	$886.10	$886.20