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 $84.64   10.320%   $93.3748   $93.37   $93.35   $93.40  
  Purchase #2 $103.73   3.212%   $107.0618   $107.06   $107.05   $107.10  
  Purchase #3 $167.77   5.238%   $176.5578   $176.56   $176.55   $176.60  
  Purchase #4 $59.63   8.477%   $64.6848   $64.68   $64.70   $64.70  
  Purchase #5 $119.99   5.294%   $126.3423   $126.34   $126.35   $126.30  
  Purchase #6 $101.49   5.154%   $106.7208   $106.72   $106.70   $106.70  
  Purchase #7 $23.61   13.513%   $26.8004   $26.80   $26.80   $26.80  
  7 purchase totals = $660.86       $701.5427   $701.53   $701.50   $701.60