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 $102.36   11.537%   $114.1693   $114.17   $114.15   $114.20  
  Purchase #2 $54.50   7.329%   $58.4943   $58.49   $58.50   $58.50  
  Purchase #3 $139.49   4.672%   $146.007   $146.01   $146.00   $146.00  
  Purchase #4 $242.81   5.559%   $256.3078   $256.31   $256.30   $256.30  
  Purchase #5 $214.80   3.439%   $222.187   $222.19   $222.20   $222.20  
  Purchase #6 $207.95   6.650%   $221.7787   $221.78   $221.80   $221.80  
  Purchase #7 $213.97   10.755%   $236.9825   $236.98   $237.00   $237.00  
  7 purchase totals = $1,175.88       $1,255.9266   $1,255.93   $1,255.95   $1,256.00