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 $58.53   9.291%   $63.968   $63.97   $63.95   $64.00  
  Purchase #2 $144.62   13.592%   $164.2768   $164.28   $164.30   $164.30  
  Purchase #3 $232.52   3.163%   $239.8746   $239.87   $239.85   $239.90  
  Purchase #4 $244.75   9.339%   $267.6072   $267.61   $267.60   $267.60  
  Purchase #5 $141.68   7.404%   $152.17   $152.17   $152.15   $152.20  
  Purchase #6 $175.61   8.503%   $190.5421   $190.54   $190.55   $190.50  
  Purchase #7 $57.46   10.860%   $63.7002   $63.70   $63.70   $63.70  
  7 purchase totals = $1,055.17       $1,142.1389   $1,142.14   $1,142.10   $1,142.20