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	$62.73	4.836%	$65.7636	$65.76	$65.75	$65.80
Purchase #2	$130.47	12.230%	$146.4265	$146.43	$146.45	$146.40
Purchase #3	$54.25	13.762%	$61.7159	$61.72	$61.70	$61.70
Purchase #4	$30.79	9.210%	$33.6258	$33.63	$33.65	$33.60
Purchase #5	$155.46	6.806%	$166.0406	$166.04	$166.05	$166.00
Purchase #6	$135.59	5.418%	$142.9363	$142.94	$142.95	$142.90
Purchase #7	$218.67	6.766%	$233.4652	$233.47	$233.45	$233.50
7 purchase totals =	$787.96		$849.9739	$849.99	$850.00	$849.90