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	$137.47	7.281%	$147.4792	$147.48	$147.50	$147.50
Purchase #2	$96.60	6.714%	$103.0857	$103.09	$103.10	$103.10
Purchase #3	$18.48	13.692%	$21.0103	$21.01	$21.00	$21.00
Purchase #4	$214.51	5.566%	$226.4496	$226.45	$226.45	$226.40
Purchase #5	$95.52	8.341%	$103.4873	$103.49	$103.50	$103.50
Purchase #6	$180.71	9.590%	$198.0401	$198.04	$198.05	$198.00
Purchase #7	$72.87	8.287%	$78.9087	$78.91	$78.90	$78.90
7 purchase totals =	$816.16		$878.4609	$878.47	$878.50	$878.40