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 $53.47   5.194%   $56.2472   $56.25   $56.25   $56.20  
  Purchase #2 $46.26   5.200%   $48.6655   $48.67   $48.65   $48.70  
  Purchase #3 $114.78   12.765%   $129.4317   $129.43   $129.45   $129.40  
  Purchase #4 $107.50   6.568%   $114.5606   $114.56   $114.55   $114.60  
  Purchase #5 $112.46   6.176%   $119.4055   $119.41   $119.40   $119.40  
  Purchase #6 $195.65   5.421%   $206.2562   $206.26   $206.25   $206.30  
  Purchase #7 $24.58   6.857%   $26.2655   $26.27   $26.25   $26.30  
  7 purchase totals = $654.70       $700.8322   $700.85   $700.80   $700.90