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 $56.58   11.174%   $62.9022   $62.90   $62.90   $62.90  
  Purchase #2 $235.99   10.519%   $260.8138   $260.81   $260.80   $260.80  
  Purchase #3 $9.79   8.668%   $10.6386   $10.64   $10.65   $10.60  
  Purchase #4 $34.27   3.774%   $35.5633   $35.56   $35.55   $35.60  
  Purchase #5 $45.60   3.459%   $47.1773   $47.18   $47.20   $47.20  
  Purchase #6 $183.65   13.195%   $207.8826   $207.88   $207.90   $207.90  
  Purchase #7 $167.94   6.720%   $179.2256   $179.23   $179.25   $179.20  
  7 purchase totals = $733.82       $804.2034   $804.20   $804.25   $804.20