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 $181.88   7.249%   $195.0645   $195.06   $195.05   $195.10  
  Purchase #2 $74.50   9.194%   $81.3495   $81.35   $81.35   $81.30  
  Purchase #3 $88.89   11.430%   $99.0501   $99.05   $99.05   $99.10  
  Purchase #4 $93.40   4.526%   $97.6273   $97.63   $97.65   $97.60  
  Purchase #5 $119.55   3.691%   $123.9626   $123.96   $123.95   $124.00  
  Purchase #6 $134.81   6.254%   $143.241   $143.24   $143.25   $143.20  
  Purchase #7 $101.77   12.752%   $114.7477   $114.75   $114.75   $114.70  
  7 purchase totals = $794.80       $855.0427   $855.04   $855.05   $855.00