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 $69.31   3.805%   $71.9472   $71.95   $71.95   $71.90  
  Purchase #2 $80.67   8.508%   $87.5334   $87.53   $87.55   $87.50  
  Purchase #3 $229.28   4.592%   $239.8085   $239.81   $239.80   $239.80  
  Purchase #4 $32.91   5.857%   $34.8375   $34.84   $34.85   $34.80  
  Purchase #5 $143.60   13.442%   $162.9027   $162.90   $162.90   $162.90  
  Purchase #6 $92.51   10.303%   $102.0413   $102.04   $102.05   $102.00  
  Purchase #7 $240.97   3.776%   $250.069   $250.07   $250.05   $250.10  
  7 purchase totals = $889.25       $949.1396   $949.14   $949.15   $949.00