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 $46.46   3.291%   $47.989   $47.99   $48.00   $48.00  
  Purchase #2 $229.27   12.144%   $257.1125   $257.11   $257.10   $257.10  
  Purchase #3 $76.99   6.283%   $81.8273   $81.83   $81.85   $81.80  
  Purchase #4 $207.94   9.844%   $228.4096   $228.41   $228.40   $228.40  
  Purchase #5 $143.42   9.800%   $157.4752   $157.48   $157.50   $157.50  
  Purchase #6 $186.39   7.855%   $201.0309   $201.03   $201.05   $201.00  
  Purchase #7 $63.47   10.842%   $70.3514   $70.35   $70.35   $70.40  
  7 purchase totals = $953.94       $1,044.1959   $1,044.20   $1,044.25   $1,044.20