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 $131.57   3.402%   $136.046   $136.05   $136.05   $136.00  
  Purchase #2 $250.25   4.552%   $261.6414   $261.64   $261.65   $261.60  
  Purchase #3 $183.96   7.509%   $197.7736   $197.77   $197.75   $197.80  
  Purchase #4 $133.73   7.445%   $143.6862   $143.69   $143.70   $143.70  
  Purchase #5 $118.78   4.274%   $123.8567   $123.86   $123.85   $123.90  
  Purchase #6 $45.44   5.626%   $47.9965   $48.00   $48.00   $48.00  
  Purchase #7 $150.67   9.479%   $164.952   $164.95   $164.95   $165.00  
  7 purchase totals = $1,014.40       $1,075.9524   $1,075.96   $1,075.95   $1,076.00