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 $23.35   11.427%   $26.0182   $26.02   $26.00   $26.00  
  Purchase #2 $122.57   5.139%   $128.8689   $128.87   $128.85   $128.90  
  Purchase #3 $169.85   6.783%   $181.3709   $181.37   $181.35   $181.40  
  Purchase #4 $242.41   8.673%   $263.4342   $263.43   $263.45   $263.40  
  Purchase #5 $62.39   13.823%   $71.0142   $71.01   $71.00   $71.00  
  Purchase #6 $230.68   13.615%   $262.0871   $262.09   $262.10   $262.10  
  Purchase #7 $14.69   3.184%   $15.1577   $15.16   $15.15   $15.20  
  7 purchase totals = $865.94       $947.9512   $947.95   $947.90   $948.00