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 $208.56   13.131%   $235.946   $235.95   $235.95   $235.90  
  Purchase #2 $165.64   11.126%   $184.0691   $184.07   $184.05   $184.10  
  Purchase #3 $72.82   4.127%   $75.8253   $75.83   $75.85   $75.80  
  Purchase #4 $111.66   11.550%   $124.5567   $124.56   $124.55   $124.60  
  Purchase #5 $232.32   9.633%   $254.6994   $254.70   $254.70   $254.70  
  Purchase #6 $177.85   10.707%   $196.8924   $196.89   $196.90   $196.90  
  Purchase #7 $239.72   8.104%   $259.1469   $259.15   $259.15   $259.10  
  7 purchase totals = $1,208.57       $1,331.1358   $1,331.15   $1,331.15   $1,331.10