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 $93.95   13.318%   $106.4623   $106.46   $106.45   $106.50  
  Purchase #2 $230.59   7.231%   $247.264   $247.26   $247.25   $247.30  
  Purchase #3 $94.25   3.606%   $97.6487   $97.65   $97.65   $97.60  
  Purchase #4 $242.56   4.657%   $253.856   $253.86   $253.85   $253.90  
  Purchase #5 $105.28   12.271%   $118.1989   $118.20   $118.20   $118.20  
  Purchase #6 $202.32   5.605%   $213.66   $213.66   $213.65   $213.70  
  Purchase #7 $159.82   3.549%   $165.492   $165.49   $165.50   $165.50  
  7 purchase totals = $1,128.77       $1,202.5819   $1,202.58   $1,202.55   $1,202.70