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 $58.46   9.586%   $64.064   $64.06   $64.05   $64.10  
  Purchase #2 $55.61   3.467%   $57.538   $57.54   $57.55   $57.50  
  Purchase #3 $70.48   9.491%   $77.1693   $77.17   $77.15   $77.20  
  Purchase #4 $95.46   8.202%   $103.2896   $103.29   $103.30   $103.30  
  Purchase #5 $218.82   5.684%   $231.2577   $231.26   $231.25   $231.30  
  Purchase #6 $109.40   3.749%   $113.5014   $113.50   $113.50   $113.50  
  Purchase #7 $78.26   10.130%   $86.1877   $86.19   $86.20   $86.20  
  7 purchase totals = $686.49       $733.0077   $733.01   $733.00   $733.10