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 $24.47   6.442%   $26.0464   $26.05   $26.05   $26.00  
  Purchase #2 $98.98   5.662%   $104.5842   $104.58   $104.60   $104.60  
  Purchase #3 $11.66   10.390%   $12.8715   $12.87   $12.85   $12.90  
  Purchase #4 $208.54   4.399%   $217.7137   $217.71   $217.70   $217.70  
  Purchase #5 $32.33   11.873%   $36.1685   $36.17   $36.15   $36.20  
  Purchase #6 $165.73   6.459%   $176.4345   $176.43   $176.45   $176.40  
  Purchase #7 $145.33   8.405%   $157.545   $157.55   $157.55   $157.50  
  7 purchase totals = $687.04       $731.3638   $731.36   $731.35   $731.30