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 $238.78   9.309%   $261.008   $261.01   $261.00   $261.00  
  Purchase #2 $52.38   10.175%   $57.7097   $57.71   $57.70   $57.70  
  Purchase #3 $6.43   11.457%   $7.1667   $7.17   $7.15   $7.20  
  Purchase #4 $232.56   6.799%   $248.3718   $248.37   $248.35   $248.40  
  Purchase #5 $209.59   9.707%   $229.9349   $229.93   $229.95   $229.90  
  Purchase #6 $100.36   3.681%   $104.0543   $104.05   $104.05   $104.10  
  Purchase #7 $102.29   3.801%   $106.178   $106.18   $106.20   $106.20  
  7 purchase totals = $942.39       $1,014.4234   $1,014.42   $1,014.40   $1,014.50