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	$215.50	10.724%	$238.6102	$238.61	$238.60	$238.60
Purchase #2	$177.55	4.608%	$185.7315	$185.73	$185.75	$185.70
Purchase #3	$196.43	4.304%	$204.8843	$204.88	$204.90	$204.90
Purchase #4	$118.71	6.344%	$126.241	$126.24	$126.25	$126.20
Purchase #5	$44.37	7.111%	$47.5252	$47.53	$47.55	$47.50
Purchase #6	$215.96	11.662%	$241.1453	$241.15	$241.15	$241.10
Purchase #7	$198.38	8.677%	$215.5934	$215.59	$215.60	$215.60
7 purchase totals =	$1,166.90		$1,259.7309	$1,259.73	$1,259.80	$1,259.60