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	$95.98	13.312%	$108.7569	$108.76	$108.75	$108.80
Purchase #2	$104.39	4.411%	$108.9946	$108.99	$109.00	$109.00
Purchase #3	$71.58	8.751%	$77.844	$77.84	$77.85	$77.80
Purchase #4	$82.94	12.766%	$93.5281	$93.53	$93.55	$93.50
Purchase #5	$135.75	4.628%	$142.0325	$142.03	$142.05	$142.00
Purchase #6	$49.84	11.443%	$55.5432	$55.54	$55.55	$55.50
Purchase #7	$183.82	7.141%	$196.9466	$196.95	$196.95	$196.90
7 purchase totals =	$724.30		$783.6459	$783.64	$783.70	$783.50