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 $66.62   11.426%   $74.232   $74.23   $74.25   $74.20  
  Purchase #2 $234.68   8.544%   $254.7311   $254.73   $254.75   $254.70  
  Purchase #3 $114.98   7.177%   $123.2321   $123.23   $123.25   $123.20  
  Purchase #4 $106.95   12.353%   $120.1615   $120.16   $120.15   $120.20  
  Purchase #5 $244.45   5.172%   $257.093   $257.09   $257.10   $257.10  
  Purchase #6 $47.88   5.230%   $50.3841   $50.38   $50.40   $50.40  
  Purchase #7 $125.44   4.784%   $131.441   $131.44   $131.45   $131.40  
  7 purchase totals = $941.00       $1,011.2748   $1,011.26   $1,011.35   $1,011.20