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 $61.66   3.716%   $63.9513   $63.95   $63.95   $64.00  
  Purchase #2 $194.61   3.178%   $200.7947   $200.79   $200.80   $200.80  
  Purchase #3 $237.69   5.223%   $250.1045   $250.10   $250.10   $250.10  
  Purchase #4 $190.55   3.182%   $196.6133   $196.61   $196.60   $196.60  
  Purchase #5 $216.46   12.686%   $243.9201   $243.92   $243.90   $243.90  
  Purchase #6 $217.82   5.686%   $230.2052   $230.21   $230.20   $230.20  
  Purchase #7 $160.93   11.521%   $179.4707   $179.47   $179.45   $179.50  
  7 purchase totals = $1,279.72       $1,365.0598   $1,365.05   $1,365.00   $1,365.10