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 $110.52   3.202%   $114.0589   $114.06   $114.05   $114.10  
  Purchase #2 $53.74   6.700%   $57.3406   $57.34   $57.35   $57.30  
  Purchase #3 $227.67   3.523%   $235.6908   $235.69   $235.70   $235.70  
  Purchase #4 $57.63   5.338%   $60.7063   $60.71   $60.70   $60.70  
  Purchase #5 $182.32   13.204%   $206.3935   $206.39   $206.40   $206.40  
  Purchase #6 $145.97   10.723%   $161.6224   $161.62   $161.60   $161.60  
  Purchase #7 $235.36   9.579%   $257.9051   $257.91   $257.90   $257.90  
  7 purchase totals = $1,013.21       $1,093.7176   $1,093.72   $1,093.70   $1,093.70