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	$161.42	11.424%	$179.8606	$179.86	$179.85	$179.90
Purchase #2	$34.71	10.586%	$38.3844	$38.38	$38.40	$38.40
Purchase #3	$174.46	9.732%	$191.4384	$191.44	$191.45	$191.40
Purchase #4	$66.60	8.863%	$72.5028	$72.50	$72.50	$72.50
Purchase #5	$154.43	13.302%	$174.9723	$174.97	$174.95	$175.00
Purchase #6	$189.29	7.315%	$203.1366	$203.14	$203.15	$203.10
Purchase #7	$104.94	6.537%	$111.7999	$111.80	$111.80	$111.80
7 purchase totals =	$885.85		$972.0950	$972.09	$972.10	$972.10