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 $24.53   8.148%   $26.5287   $26.53   $26.55   $26.50  
  Purchase #2 $179.75   9.205%   $196.296   $196.30   $196.30   $196.30  
  Purchase #3 $228.62   4.448%   $238.789   $238.79   $238.80   $238.80  
  Purchase #4 $125.29   8.667%   $136.1489   $136.15   $136.15   $136.10  
  Purchase #5 $140.36   6.156%   $149.0006   $149.00   $149.00   $149.00  
  Purchase #6 $185.25   4.319%   $193.2509   $193.25   $193.25   $193.30  
  Purchase #7 $14.56   4.481%   $15.2124   $15.21   $15.20   $15.20  
  7 purchase totals = $898.36       $955.2265   $955.23   $955.25   $955.20