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	$84.84	12.817%	$95.7139	$95.71	$95.70	$95.70
Purchase #2	$42.29	6.549%	$45.0596	$45.06	$45.05	$45.10
Purchase #3	$150.27	5.699%	$158.8339	$158.83	$158.85	$158.80
Purchase #4	$124.82	12.819%	$140.8207	$140.82	$140.80	$140.80
Purchase #5	$82.29	10.360%	$90.8152	$90.82	$90.80	$90.80
Purchase #6	$126.28	9.693%	$138.5203	$138.52	$138.50	$138.50
Purchase #7	$166.29	6.297%	$176.7613	$176.76	$176.75	$176.80
7 purchase totals =	$777.08		$846.5249	$846.52	$846.45	$846.50