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 $82.57   13.416%   $93.6476   $93.65   $93.65   $93.60  
  Purchase #2 $173.69   11.278%   $193.2788   $193.28   $193.30   $193.30  
  Purchase #3 $14.71   10.634%   $16.2743   $16.27   $16.25   $16.30  
  Purchase #4 $235.67   9.857%   $258.9   $258.90   $258.90   $258.90  
  Purchase #5 $217.46   5.297%   $228.9789   $228.98   $229.00   $229.00  
  Purchase #6 $121.98   4.653%   $127.6557   $127.66   $127.65   $127.70  
  Purchase #7 $89.41   3.154%   $92.23   $92.23   $92.25   $92.20  
  7 purchase totals = $935.49       $1,010.9653   $1,010.97   $1,011.00   $1,011.00