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 $111.60   5.861%   $118.1409   $118.14   $118.15   $118.10  
  Purchase #2 $55.71   4.822%   $58.3963   $58.40   $58.40   $58.40  
  Purchase #3 $180.53   12.717%   $203.488   $203.49   $203.50   $203.50  
  Purchase #4 $166.54   8.452%   $180.616   $180.62   $180.60   $180.60  
  Purchase #5 $169.73   5.618%   $179.2654   $179.27   $179.25   $179.30  
  Purchase #6 $208.35   13.466%   $236.4064   $236.41   $236.40   $236.40  
  Purchase #7 $134.95   10.204%   $148.7203   $148.72   $148.70   $148.70  
  7 purchase totals = $1,027.41       $1,125.0333   $1,125.05   $1,125.00   $1,125.00