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 $84.42   12.707%   $95.1472   $95.15   $95.15   $95.10  
  Purchase #2 $101.38   7.601%   $109.0859   $109.09   $109.10   $109.10  
  Purchase #3 $176.56   13.612%   $200.5933   $200.59   $200.60   $200.60  
  Purchase #4 $9.40   3.691%   $9.747   $9.75   $9.75   $9.70  
  Purchase #5 $168.32   8.143%   $182.0263   $182.03   $182.05   $182.00  
  Purchase #6 $205.40   3.279%   $212.1351   $212.14   $212.15   $212.10  
  Purchase #7 $122.61   3.118%   $126.433   $126.43   $126.45   $126.40  
  7 purchase totals = $868.09       $935.1678   $935.18   $935.25   $935.00