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	$32.95	13.190%	$37.2961	$37.30	$37.30	$37.30
Purchase #2	$182.38	7.247%	$195.5971	$195.60	$195.60	$195.60
Purchase #3	$242.79	5.615%	$256.4227	$256.42	$256.40	$256.40
Purchase #4	$115.25	13.745%	$131.0911	$131.09	$131.10	$131.10
Purchase #5	$13.38	13.507%	$15.1872	$15.19	$15.20	$15.20
Purchase #6	$134.41	3.107%	$138.5861	$138.59	$138.60	$138.60
Purchase #7	$99.72	11.789%	$111.476	$111.48	$111.50	$111.50
7 purchase totals =	$820.88		$885.6563	$885.67	$885.70	$885.70