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 $43.70   9.759%   $47.9647   $47.96   $47.95   $48.00  
  Purchase #2 $236.64   10.843%   $262.2989   $262.30   $262.30   $262.30  
  Purchase #3 $51.86   11.137%   $57.6356   $57.64   $57.65   $57.60  
  Purchase #4 $179.27   8.814%   $195.0709   $195.07   $195.05   $195.10  
  Purchase #5 $56.68   3.529%   $58.6802   $58.68   $58.70   $58.70  
  Purchase #6 $155.27   5.531%   $163.858   $163.86   $163.85   $163.90  
  Purchase #7 $224.30   8.796%   $244.0294   $244.03   $244.05   $244.00  
  7 purchase totals = $947.72       $1,029.5377   $1,029.54   $1,029.55   $1,029.60