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	$76.43	10.824%	$84.7028	$84.70	$84.70	$84.70
Purchase #2	$131.33	9.824%	$144.2319	$144.23	$144.25	$144.20
Purchase #3	$66.82	6.794%	$71.3598	$71.36	$71.35	$71.40
Purchase #4	$131.88	8.801%	$143.4868	$143.49	$143.50	$143.50
Purchase #5	$204.39	5.443%	$215.5149	$215.51	$215.50	$215.50
Purchase #6	$198.79	8.204%	$215.0987	$215.10	$215.10	$215.10
Purchase #7	$212.95	12.105%	$238.7276	$238.73	$238.75	$238.70
7 purchase totals =	$1,022.59		$1,113.1225	$1,113.12	$1,113.15	$1,113.10