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 $87.56   8.404%   $94.9185   $94.92   $94.90   $94.90  
  Purchase #2 $177.86   13.681%   $202.193   $202.19   $202.20   $202.20  
  Purchase #3 $146.57   9.560%   $160.5821   $160.58   $160.60   $160.60  
  Purchase #4 $113.60   8.624%   $123.3969   $123.40   $123.40   $123.40  
  Purchase #5 $126.69   13.861%   $144.2505   $144.25   $144.25   $144.30  
  Purchase #6 $84.78   12.140%   $95.0723   $95.07   $95.05   $95.10  
  Purchase #7 $128.91   4.438%   $134.631   $134.63   $134.65   $134.60  
  7 purchase totals = $865.97       $955.0443   $955.04   $955.05   $955.10