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	$87.28	9.486%	$95.5594	$95.56	$95.55	$95.60
Purchase #2	$199.64	4.650%	$208.9233	$208.92	$208.90	$208.90
Purchase #3	$240.28	3.576%	$248.8724	$248.87	$248.85	$248.90
Purchase #4	$216.97	6.828%	$231.7847	$231.78	$231.80	$231.80
Purchase #5	$87.30	3.532%	$90.3834	$90.38	$90.40	$90.40
Purchase #6	$43.94	13.329%	$49.7968	$49.80	$49.80	$49.80
Purchase #7	$38.92	9.372%	$42.5676	$42.57	$42.55	$42.60
7 purchase totals =	$914.33		$967.8876	$967.88	$967.85	$968.00