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	$38.70	12.397%	$43.4976	$43.50	$43.50	$43.50
Purchase #2	$164.90	11.396%	$183.692	$183.69	$183.70	$183.70
Purchase #3	$128.84	10.482%	$142.345	$142.35	$142.35	$142.30
Purchase #4	$13.38	12.754%	$15.0865	$15.09	$15.10	$15.10
Purchase #5	$224.46	7.507%	$241.3102	$241.31	$241.30	$241.30
Purchase #6	$172.78	7.153%	$185.139	$185.14	$185.15	$185.10
Purchase #7	$238.30	10.863%	$264.1865	$264.19	$264.20	$264.20
7 purchase totals =	$981.36		$1,075.2568	$1,075.27	$1,075.30	$1,075.20