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 $192.87   4.223%   $201.0149   $201.01   $201.00   $201.00  
  Purchase #2 $169.29   3.609%   $175.3997   $175.40   $175.40   $175.40  
  Purchase #3 $11.28   5.673%   $11.9199   $11.92   $11.90   $11.90  
  Purchase #4 $177.73   12.753%   $200.3959   $200.40   $200.40   $200.40  
  Purchase #5 $121.46   10.164%   $133.8052   $133.81   $133.80   $133.80  
  Purchase #6 $32.36   9.441%   $35.4151   $35.42   $35.40   $35.40  
  Purchase #7 $201.51   3.762%   $209.0908   $209.09   $209.10   $209.10  
  7 purchase totals = $906.50       $967.0415   $967.05   $967.00   $967.00