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 $87.79   8.845%   $95.555   $95.56   $95.55   $95.60  
  Purchase #2 $164.82   13.335%   $186.7987   $186.80   $186.80   $186.80  
  Purchase #3 $125.64   8.502%   $136.3219   $136.32   $136.30   $136.30  
  Purchase #4 $136.65   5.728%   $144.4773   $144.48   $144.50   $144.50  
  Purchase #5 $159.38   9.861%   $175.0965   $175.10   $175.10   $175.10  
  Purchase #6 $205.28   5.126%   $215.8027   $215.80   $215.80   $215.80  
  Purchase #7 $56.51   11.499%   $63.0081   $63.01   $63.00   $63.00  
  7 purchase totals = $936.07       $1,017.0602   $1,017.07   $1,017.05   $1,017.10