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 $69.26   3.862%   $71.9348   $71.93   $71.95   $71.90  
  Purchase #2 $31.88   5.697%   $33.6962   $33.70   $33.70   $33.70  
  Purchase #3 $109.51   3.451%   $113.2892   $113.29   $113.30   $113.30  
  Purchase #4 $242.77   10.870%   $269.1591   $269.16   $269.15   $269.20  
  Purchase #5 $47.40   12.378%   $53.2672   $53.27   $53.25   $53.30  
  Purchase #6 $242.41   4.738%   $253.8954   $253.90   $253.90   $253.90  
  Purchase #7 $148.71   10.261%   $163.9691   $163.97   $163.95   $164.00  
  7 purchase totals = $891.94       $959.2110   $959.22   $959.20   $959.30