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 $66.46   12.726%   $74.9177   $74.92   $74.90   $74.90  
  Purchase #2 $136.41   13.831%   $155.2769   $155.28   $155.30   $155.30  
  Purchase #3 $78.95   13.602%   $89.6888   $89.69   $89.70   $89.70  
  Purchase #4 $214.76   7.495%   $230.8563   $230.86   $230.85   $230.90  
  Purchase #5 $204.65   9.588%   $224.2718   $224.27   $224.25   $224.30  
  Purchase #6 $162.67   7.387%   $174.6864   $174.69   $174.70   $174.70  
  Purchase #7 $172.75   7.417%   $185.5629   $185.56   $185.55   $185.60  
  7 purchase totals = $1,036.65       $1,135.2608   $1,135.27   $1,135.25   $1,135.40