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	$45.44	6.728%	$48.4972	$48.50	$48.50	$48.50
Purchase #2	$205.51	11.180%	$228.486	$228.49	$228.50	$228.50
Purchase #3	$211.60	7.499%	$227.4679	$227.47	$227.45	$227.50
Purchase #4	$52.64	13.782%	$59.8948	$59.89	$59.90	$59.90
Purchase #5	$166.92	3.529%	$172.8106	$172.81	$172.80	$172.80
Purchase #6	$75.57	3.838%	$78.4704	$78.47	$78.45	$78.50
Purchase #7	$199.49	10.704%	$220.8434	$220.84	$220.85	$220.80
7 purchase totals =	$957.17		$1,036.4703	$1,036.47	$1,036.45	$1,036.50