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	$131.31	9.444%	$143.7109	$143.71	$143.70	$143.70
Purchase #2	$113.86	9.419%	$124.5845	$124.58	$124.60	$124.60
Purchase #3	$94.25	5.172%	$99.1246	$99.12	$99.10	$99.10
Purchase #4	$118.66	4.509%	$124.0104	$124.01	$124.00	$124.00
Purchase #5	$191.25	4.767%	$200.3669	$200.37	$200.35	$200.40
Purchase #6	$208.89	4.486%	$218.2608	$218.26	$218.25	$218.30
Purchase #7	$32.60	10.589%	$36.052	$36.05	$36.05	$36.10
7 purchase totals =	$890.82		$946.1101	$946.10	$946.05	$946.20