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 $103.52   10.836%   $114.7374   $114.74   $114.75   $114.70  
  Purchase #2 $250.60   5.208%   $263.6512   $263.65   $263.65   $263.70  
  Purchase #3 $167.37   10.456%   $184.8702   $184.87   $184.85   $184.90  
  Purchase #4 $54.26   7.243%   $58.1901   $58.19   $58.20   $58.20  
  Purchase #5 $44.81   4.604%   $46.8731   $46.87   $46.85   $46.90  
  Purchase #6 $137.47   5.189%   $144.6033   $144.60   $144.60   $144.60  
  Purchase #7 $124.72   7.292%   $133.8146   $133.81   $133.80   $133.80  
  7 purchase totals = $882.75       $946.7399   $946.73   $946.70   $946.80