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	$90.50	12.403%	$101.7247	$101.72	$101.70	$101.70
Purchase #2	$112.83	9.541%	$123.5951	$123.60	$123.60	$123.60
Purchase #3	$234.95	11.724%	$262.4955	$262.50	$262.50	$262.50
Purchase #4	$44.87	7.324%	$48.1563	$48.16	$48.15	$48.20
Purchase #5	$237.78	7.540%	$255.7086	$255.71	$255.70	$255.70
Purchase #6	$100.81	6.298%	$107.159	$107.16	$107.15	$107.20
Purchase #7	$150.63	10.277%	$166.1102	$166.11	$166.10	$166.10
7 purchase totals =	$972.37		$1,064.9494	$1,064.96	$1,064.90	$1,065.00