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 $89.54   6.310%   $95.19   $95.19   $95.20   $95.20  
  Purchase #2 $239.29   4.621%   $250.3476   $250.35   $250.35   $250.30  
  Purchase #3 $139.27   7.661%   $149.9395   $149.94   $149.95   $149.90  
  Purchase #4 $145.50   13.348%   $164.9213   $164.92   $164.90   $164.90  
  Purchase #5 $163.33   6.444%   $173.855   $173.86   $173.85   $173.90  
  Purchase #6 $239.76   9.127%   $261.6429   $261.64   $261.65   $261.60  
  Purchase #7 $106.59   6.175%   $113.1719   $113.17   $113.15   $113.20  
  7 purchase totals = $1,123.28       $1,209.0682   $1,209.07   $1,209.05   $1,209.00