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 $44.95   4.659%   $47.0442   $47.04   $47.05   $47.00  
  Purchase #2 $95.58   12.215%   $107.2551   $107.26   $107.25   $107.30  
  Purchase #3 $61.94   9.676%   $67.9333   $67.93   $67.95   $67.90  
  Purchase #4 $182.37   5.211%   $191.8733   $191.87   $191.85   $191.90  
  Purchase #5 $240.54   8.433%   $260.8247   $260.82   $260.80   $260.80  
  Purchase #6 $117.64   13.467%   $133.4826   $133.48   $133.50   $133.50  
  Purchase #7 $106.37   12.505%   $119.6716   $119.67   $119.65   $119.70  
  7 purchase totals = $849.39       $928.0848   $928.07   $928.05   $928.10