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 $104.71   13.594%   $118.9443   $118.94   $118.95   $118.90  
  Purchase #2 $44.34   12.646%   $49.9472   $49.95   $49.95   $49.90  
  Purchase #3 $119.57   4.675%   $125.1599   $125.16   $125.15   $125.20  
  Purchase #4 $144.26   8.259%   $156.1744   $156.17   $156.15   $156.20  
  Purchase #5 $145.96   11.419%   $162.6272   $162.63   $162.65   $162.60  
  Purchase #6 $134.60   3.229%   $138.9462   $138.95   $138.95   $138.90  
  Purchase #7 $127.66   12.644%   $143.8013   $143.80   $143.80   $143.80  
  7 purchase totals = $821.10       $895.6005   $895.60   $895.60   $895.50