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 $24.77   5.741%   $26.192   $26.19   $26.20   $26.20  
  Purchase #2 $220.92   9.872%   $242.7292   $242.73   $242.75   $242.70  
  Purchase #3 $62.47   8.833%   $67.988   $67.99   $68.00   $68.00  
  Purchase #4 $143.34   7.299%   $153.8024   $153.80   $153.80   $153.80  
  Purchase #5 $237.37   6.515%   $252.8347   $252.83   $252.85   $252.80  
  Purchase #6 $174.56   10.794%   $193.402   $193.40   $193.40   $193.40  
  Purchase #7 $225.90   7.513%   $242.8719   $242.87   $242.85   $242.90  
  7 purchase totals = $1,089.33       $1,179.8202   $1,179.81   $1,179.85   $1,179.80