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 $105.79   6.116%   $112.2601   $112.26   $112.25   $112.30  
  Purchase #2 $239.53   5.298%   $252.2203   $252.22   $252.20   $252.20  
  Purchase #3 $22.65   5.433%   $23.8806   $23.88   $23.90   $23.90  
  Purchase #4 $86.87   7.871%   $93.7075   $93.71   $93.70   $93.70  
  Purchase #5 $175.96   11.577%   $196.3309   $196.33   $196.35   $196.30  
  Purchase #6 $102.94   11.572%   $114.8522   $114.85   $114.85   $114.90  
  Purchase #7 $194.82   4.305%   $203.207   $203.21   $203.20   $203.20  
  7 purchase totals = $928.56       $996.4586   $996.46   $996.45   $996.50