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 $196.66   5.214%   $206.9139   $206.91   $206.90   $206.90  
  Purchase #2 $154.56   6.606%   $164.7702   $164.77   $164.75   $164.80  
  Purchase #3 $224.52   4.821%   $235.3441   $235.34   $235.35   $235.30  
  Purchase #4 $28.33   7.337%   $30.4086   $30.41   $30.40   $30.40  
  Purchase #5 $120.35   13.595%   $136.7116   $136.71   $136.70   $136.70  
  Purchase #6 $212.47   10.602%   $234.9961   $235.00   $235.00   $235.00  
  Purchase #7 $46.72   4.702%   $48.9168   $48.92   $48.90   $48.90  
  7 purchase totals = $983.61       $1,058.0613   $1,058.06   $1,058.00   $1,058.00