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 $84.48   12.585%   $95.1118   $95.11   $95.10   $95.10  
  Purchase #2 $58.82   5.757%   $62.2063   $62.21   $62.20   $62.20  
  Purchase #3 $121.68   10.665%   $134.6572   $134.66   $134.65   $134.70  
  Purchase #4 $20.37   12.718%   $22.9607   $22.96   $22.95   $23.00  
  Purchase #5 $34.58   12.215%   $38.8039   $38.80   $38.80   $38.80  
  Purchase #6 $142.71   6.576%   $152.0946   $152.09   $152.10   $152.10  
  Purchase #7 $208.43   5.661%   $220.2292   $220.23   $220.25   $220.20  
  7 purchase totals = $671.07       $726.0637   $726.06   $726.05   $726.10