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 $86.77   10.323%   $95.7273   $95.73   $95.75   $95.70  
  Purchase #2 $227.26   11.766%   $253.9994   $254.00   $254.00   $254.00  
  Purchase #3 $107.68   12.681%   $121.3349   $121.33   $121.35   $121.30  
  Purchase #4 $162.39   4.843%   $170.2545   $170.25   $170.25   $170.30  
  Purchase #5 $130.26   9.621%   $142.7923   $142.79   $142.80   $142.80  
  Purchase #6 $12.72   3.729%   $13.1943   $13.19   $13.20   $13.20  
  Purchase #7 $232.89   12.231%   $261.3748   $261.37   $261.35   $261.40  
  7 purchase totals = $959.97       $1,058.6775   $1,058.66   $1,058.70   $1,058.70