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 $157.71   11.344%   $175.6006   $175.60   $175.60   $175.60  
  Purchase #2 $208.71   9.376%   $228.2786   $228.28   $228.30   $228.30  
  Purchase #3 $109.37   4.761%   $114.5771   $114.58   $114.60   $114.60  
  Purchase #4 $10.34   11.154%   $11.4933   $11.49   $11.50   $11.50  
  Purchase #5 $207.70   13.118%   $234.9461   $234.95   $234.95   $234.90  
  Purchase #6 $133.31   6.593%   $142.0991   $142.10   $142.10   $142.10  
  Purchase #7 $249.25   4.413%   $260.2494   $260.25   $260.25   $260.20  
  7 purchase totals = $1,076.39       $1,167.2442   $1,167.25   $1,167.30   $1,167.20