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 $192.46   4.549%   $201.215   $201.22   $201.20   $201.20  
  Purchase #2 $15.81   9.342%   $17.287   $17.29   $17.30   $17.30  
  Purchase #3 $189.61   4.456%   $198.059   $198.06   $198.05   $198.10  
  Purchase #4 $236.43   10.621%   $261.5412   $261.54   $261.55   $261.50  
  Purchase #5 $39.99   3.692%   $41.4664   $41.47   $41.45   $41.50  
  Purchase #6 $245.38   8.173%   $265.4349   $265.43   $265.45   $265.40  
  Purchase #7 $26.97   9.135%   $29.4337   $29.43   $29.45   $29.40  
  7 purchase totals = $946.65       $1,014.4372   $1,014.44   $1,014.45   $1,014.40