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 $90.76   5.499%   $95.7509   $95.75   $95.75   $95.80  
  Purchase #2 $82.79   10.497%   $91.4805   $91.48   $91.50   $91.50  
  Purchase #3 $191.29   13.667%   $217.4336   $217.43   $217.45   $217.40  
  Purchase #4 $177.79   12.292%   $199.6439   $199.64   $199.65   $199.60  
  Purchase #5 $77.96   10.277%   $85.9719   $85.97   $85.95   $86.00  
  Purchase #6 $250.97   4.194%   $261.4957   $261.50   $261.50   $261.50  
  Purchase #7 $78.36   4.205%   $81.655   $81.66   $81.65   $81.70  
  7 purchase totals = $949.92       $1,033.4315   $1,033.43   $1,033.45   $1,033.50