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	$206.76	5.233%	$217.5798	$217.58	$217.60	$217.60
Purchase #2	$242.87	7.261%	$260.5048	$260.50	$260.50	$260.50
Purchase #3	$183.42	12.168%	$205.7385	$205.74	$205.75	$205.70
Purchase #4	$116.39	13.849%	$132.5089	$132.51	$132.50	$132.50
Purchase #5	$85.96	7.199%	$92.1483	$92.15	$92.15	$92.10
Purchase #6	$71.33	9.481%	$78.0928	$78.09	$78.10	$78.10
Purchase #7	$20.41	4.353%	$21.2984	$21.30	$21.30	$21.30
7 purchase totals =	$927.14		$1,007.8715	$1,007.87	$1,007.90	$1,007.80