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 $205.87   11.360%   $229.2568   $229.26   $229.25   $229.30  
  Purchase #2 $174.57   10.754%   $193.3433   $193.34   $193.35   $193.30  
  Purchase #3 $150.64   4.453%   $157.348   $157.35   $157.35   $157.30  
  Purchase #4 $73.71   4.394%   $76.9488   $76.95   $76.95   $76.90  
  Purchase #5 $38.34   8.122%   $41.454   $41.45   $41.45   $41.50  
  Purchase #6 $112.30   3.581%   $116.3215   $116.32   $116.30   $116.30  
  Purchase #7 $77.63   4.719%   $81.2934   $81.29   $81.30   $81.30  
  7 purchase totals = $833.06       $895.9658   $895.96   $895.95   $895.90