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	$87.85	6.413%	$93.4838	$93.48	$93.50	$93.50
Purchase #2	$56.72	13.781%	$64.5366	$64.54	$64.55	$64.50
Purchase #3	$196.42	11.294%	$218.6037	$218.60	$218.60	$218.60
Purchase #4	$217.31	13.283%	$246.1753	$246.18	$246.20	$246.20
Purchase #5	$236.86	5.339%	$249.506	$249.51	$249.50	$249.50
Purchase #6	$90.37	4.547%	$94.4791	$94.48	$94.50	$94.50
Purchase #7	$178.47	3.143%	$184.0793	$184.08	$184.10	$184.10
7 purchase totals =	$1,064.00		$1,150.8638	$1,150.87	$1,150.95	$1,150.90