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 $56.61   4.728%   $59.2865   $59.29   $59.30   $59.30  
  Purchase #2 $207.53   3.253%   $214.281   $214.28   $214.30   $214.30  
  Purchase #3 $10.48   8.862%   $11.4087   $11.41   $11.40   $11.40  
  Purchase #4 $90.72   4.726%   $95.0074   $95.01   $95.00   $95.00  
  Purchase #5 $24.68   5.288%   $25.9851   $25.99   $26.00   $26.00  
  Purchase #6 $205.33   4.237%   $214.0298   $214.03   $214.05   $214.00  
  Purchase #7 $86.54   12.548%   $97.399   $97.40   $97.40   $97.40  
  7 purchase totals = $681.89       $717.3975   $717.41   $717.45   $717.40