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 $160.57   13.811%   $182.7463   $182.75   $182.75   $182.70  
  Purchase #2 $222.89   5.119%   $234.2997   $234.30   $234.30   $234.30  
  Purchase #3 $125.99   8.709%   $136.9625   $136.96   $136.95   $137.00  
  Purchase #4 $206.45   5.435%   $217.6706   $217.67   $217.65   $217.70  
  Purchase #5 $55.91   3.651%   $57.9513   $57.95   $57.95   $58.00  
  Purchase #6 $70.40   13.273%   $79.7442   $79.74   $79.75   $79.70  
  Purchase #7 $159.58   3.826%   $165.6855   $165.69   $165.70   $165.70  
  7 purchase totals = $1,001.79       $1,075.0601   $1,075.06   $1,075.05   $1,075.10