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 $41.71   12.569%   $46.9525   $46.95   $46.95   $47.00  
  Purchase #2 $144.45   7.238%   $154.9053   $154.91   $154.90   $154.90  
  Purchase #3 $48.94   6.672%   $52.2053   $52.21   $52.20   $52.20  
  Purchase #4 $204.84   4.337%   $213.7239   $213.72   $213.70   $213.70  
  Purchase #5 $82.87   4.282%   $86.4185   $86.42   $86.40   $86.40  
  Purchase #6 $115.81   5.189%   $121.8194   $121.82   $121.80   $121.80  
  Purchase #7 $195.56   5.333%   $205.9892   $205.99   $206.00   $206.00  
  7 purchase totals = $834.18       $882.0141   $882.02   $881.95   $882.00