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	$82.51	9.824%	$90.6158	$90.62	$90.60	$90.60
Purchase #2	$111.65	3.444%	$115.4952	$115.50	$115.50	$115.50
Purchase #3	$16.40	7.340%	$17.6038	$17.60	$17.60	$17.60
Purchase #4	$32.74	12.126%	$36.7101	$36.71	$36.70	$36.70
Purchase #5	$59.55	8.403%	$64.554	$64.55	$64.55	$64.60
Purchase #6	$98.84	5.775%	$104.548	$104.55	$104.55	$104.50
Purchase #7	$137.83	3.313%	$142.3963	$142.40	$142.40	$142.40
7 purchase totals =	$539.52		$571.9232	$571.93	$571.90	$571.90