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 $219.30   9.258%   $239.6028   $239.60   $239.60   $239.60  
  Purchase #2 $87.42   12.822%   $98.629   $98.63   $98.65   $98.60  
  Purchase #3 $97.80   6.611%   $104.2656   $104.27   $104.25   $104.30  
  Purchase #4 $182.57   9.379%   $199.6932   $199.69   $199.70   $199.70  
  Purchase #5 $186.37   10.188%   $205.3574   $205.36   $205.35   $205.40  
  Purchase #6 $111.76   5.601%   $118.0197   $118.02   $118.00   $118.00  
  Purchase #7 $62.45   7.219%   $66.9583   $66.96   $66.95   $67.00  
  7 purchase totals = $947.67       $1,032.5260   $1,032.53   $1,032.50   $1,032.60