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 $199.66   3.312%   $206.2727   $206.27   $206.25   $206.30  
  Purchase #2 $148.57   8.795%   $161.6367   $161.64   $161.65   $161.60  
  Purchase #3 $68.27   5.616%   $72.104   $72.10   $72.10   $72.10  
  Purchase #4 $179.27   13.619%   $203.6848   $203.68   $203.70   $203.70  
  Purchase #5 $54.95   4.209%   $57.2628   $57.26   $57.25   $57.30  
  Purchase #6 $205.48   13.709%   $233.6493   $233.65   $233.65   $233.60  
  Purchase #7 $159.60   11.560%   $178.0498   $178.05   $178.05   $178.00  
  7 purchase totals = $1,015.80       $1,112.6601   $1,112.65   $1,112.65   $1,112.60