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 $141.92   10.756%   $157.1849   $157.18   $157.20   $157.20  
  Purchase #2 $161.61   12.746%   $182.2088   $182.21   $182.20   $182.20  
  Purchase #3 $197.75   9.737%   $217.0049   $217.00   $217.00   $217.00  
  Purchase #4 $208.68   9.649%   $228.8155   $228.82   $228.80   $228.80  
  Purchase #5 $34.40   4.564%   $35.97   $35.97   $35.95   $36.00  
  Purchase #6 $40.75   7.770%   $43.9163   $43.92   $43.90   $43.90  
  Purchase #7 $200.45   5.515%   $211.5048   $211.50   $211.50   $211.50  
  7 purchase totals = $985.56       $1,076.6052   $1,076.60   $1,076.55   $1,076.60