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	$99.42	12.532%	$111.8793	$111.88	$111.90	$111.90
Purchase #2	$45.81	4.565%	$47.9012	$47.90	$47.90	$47.90
Purchase #3	$128.99	3.469%	$133.4647	$133.46	$133.45	$133.50
Purchase #4	$201.93	5.692%	$213.4239	$213.42	$213.40	$213.40
Purchase #5	$179.61	13.264%	$203.4335	$203.43	$203.45	$203.40
Purchase #6	$196.93	8.859%	$214.376	$214.38	$214.40	$214.40
Purchase #7	$166.60	4.134%	$173.4872	$173.49	$173.50	$173.50
7 purchase totals =	$1,019.29		$1,097.9658	$1,097.96	$1,098.00	$1,098.00