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 $196.88   5.754%   $208.2085   $208.21   $208.20   $208.20  
  Purchase #2 $217.41   6.335%   $231.1829   $231.18   $231.20   $231.20  
  Purchase #3 $25.26   4.804%   $26.4735   $26.47   $26.45   $26.50  
  Purchase #4 $131.78   11.191%   $146.5275   $146.53   $146.55   $146.50  
  Purchase #5 $59.42   6.635%   $63.3625   $63.36   $63.35   $63.40  
  Purchase #6 $74.57   12.833%   $84.1396   $84.14   $84.15   $84.10  
  Purchase #7 $236.63   5.725%   $250.1771   $250.18   $250.20   $250.20  
  7 purchase totals = $941.95       $1,010.0716   $1,010.07   $1,010.10   $1,010.10