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 $161.58   8.454%   $175.24   $175.24   $175.25   $175.20  
  Purchase #2 $210.48   6.868%   $224.9358   $224.94   $224.95   $224.90  
  Purchase #3 $145.80   7.551%   $156.8094   $156.81   $156.80   $156.80  
  Purchase #4 $113.76   3.179%   $117.3764   $117.38   $117.40   $117.40  
  Purchase #5 $234.31   5.366%   $246.8831   $246.88   $246.90   $246.90  
  Purchase #6 $177.42   11.650%   $198.0894   $198.09   $198.10   $198.10  
  Purchase #7 $79.97   10.291%   $88.1997   $88.20   $88.20   $88.20  
  7 purchase totals = $1,123.32       $1,207.5338   $1,207.54   $1,207.60   $1,207.50