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 $214.75   10.182%   $236.6158   $236.62   $236.60   $236.60  
  Purchase #2 $85.41   10.739%   $94.5822   $94.58   $94.60   $94.60  
  Purchase #3 $38.95   12.196%   $43.7003   $43.70   $43.70   $43.70  
  Purchase #4 $107.58   3.224%   $111.0484   $111.05   $111.05   $111.00  
  Purchase #5 $56.57   7.268%   $60.6815   $60.68   $60.70   $60.70  
  Purchase #6 $112.78   4.394%   $117.7356   $117.74   $117.75   $117.70  
  Purchase #7 $81.48   12.393%   $91.5778   $91.58   $91.60   $91.60  
  7 purchase totals = $697.52       $755.9416   $755.95   $756.00   $755.90