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 $195.61   3.241%   $201.9497   $201.95   $201.95   $201.90  
  Purchase #2 $248.68   12.645%   $280.1256   $280.13   $280.15   $280.10  
  Purchase #3 $125.30   4.331%   $130.7267   $130.73   $130.75   $130.70  
  Purchase #4 $46.25   5.124%   $48.6199   $48.62   $48.60   $48.60  
  Purchase #5 $241.96   6.493%   $257.6705   $257.67   $257.65   $257.70  
  Purchase #6 $52.36   4.711%   $54.8267   $54.83   $54.85   $54.80  
  Purchase #7 $250.26   12.807%   $282.3108   $282.31   $282.30   $282.30  
  7 purchase totals = $1,160.42       $1,256.2299   $1,256.24   $1,256.25   $1,256.10