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	$38.25	5.334%	$40.2903	$40.29	$40.30	$40.30
Purchase #2	$44.36	4.786%	$46.4831	$46.48	$46.50	$46.50
Purchase #3	$138.90	12.266%	$155.9375	$155.94	$155.95	$155.90
Purchase #4	$148.78	11.592%	$166.0266	$166.03	$166.05	$166.00
Purchase #5	$115.37	13.189%	$130.5861	$130.59	$130.60	$130.60
Purchase #6	$198.27	9.666%	$217.4348	$217.43	$217.45	$217.40
Purchase #7	$237.98	12.286%	$267.2182	$267.22	$267.20	$267.20
7 purchase totals =	$921.91		$1,023.9766	$1,023.98	$1,024.05	$1,023.90