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	$46.42	3.872%	$48.2174	$48.22	$48.20	$48.20
Purchase #2	$240.45	13.266%	$272.3481	$272.35	$272.35	$272.30
Purchase #3	$61.94	10.594%	$68.5019	$68.50	$68.50	$68.50
Purchase #4	$243.75	7.732%	$262.5968	$262.60	$262.60	$262.60
Purchase #5	$59.30	13.670%	$67.4063	$67.41	$67.40	$67.40
Purchase #6	$200.99	7.683%	$216.4321	$216.43	$216.45	$216.40
Purchase #7	$100.67	12.138%	$112.8893	$112.89	$112.90	$112.90
7 purchase totals =	$953.52		$1,048.3919	$1,048.40	$1,048.40	$1,048.30