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 $219.85   9.744%   $241.2722   $241.27   $241.25   $241.30  
  Purchase #2 $33.68   5.145%   $35.4128   $35.41   $35.40   $35.40  
  Purchase #3 $242.50   7.618%   $260.9737   $260.97   $260.95   $261.00  
  Purchase #4 $231.61   13.134%   $262.0297   $262.03   $262.05   $262.00  
  Purchase #5 $169.90   12.800%   $191.6472   $191.65   $191.65   $191.60  
  Purchase #6 $25.85   6.333%   $27.4871   $27.49   $27.50   $27.50  
  Purchase #7 $42.78   3.158%   $44.131   $44.13   $44.15   $44.10  
  7 purchase totals = $966.17       $1,062.9537   $1,062.95   $1,062.95   $1,062.90