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	$241.62	5.757%	$255.5301	$255.53	$255.55	$255.50
Purchase #2	$200.47	3.449%	$207.3842	$207.38	$207.40	$207.40
Purchase #3	$177.94	10.523%	$196.6646	$196.66	$196.65	$196.70
Purchase #4	$62.60	13.511%	$71.0579	$71.06	$71.05	$71.10
Purchase #5	$232.67	13.373%	$263.785	$263.79	$263.80	$263.80
Purchase #6	$81.58	4.355%	$85.1328	$85.13	$85.15	$85.10
Purchase #7	$6.69	11.242%	$7.4421	$7.44	$7.45	$7.40
7 purchase totals =	$1,003.57		$1,086.9967	$1,086.99	$1,087.05	$1,087.00