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 $73.46   11.863%   $82.1746   $82.17   $82.15   $82.20  
  Purchase #2 $194.61   3.459%   $201.3416   $201.34   $201.35   $201.30  
  Purchase #3 $234.78   11.362%   $261.4557   $261.46   $261.45   $261.50  
  Purchase #4 $122.39   6.503%   $130.349   $130.35   $130.35   $130.30  
  Purchase #5 $49.83   5.197%   $52.4197   $52.42   $52.40   $52.40  
  Purchase #6 $102.40   11.143%   $113.8104   $113.81   $113.80   $113.80  
  Purchase #7 $177.73   4.270%   $185.3191   $185.32   $185.30   $185.30  
  7 purchase totals = $955.20       $1,026.8701   $1,026.87   $1,026.80   $1,026.80