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 $163.42   11.788%   $182.6839   $182.68   $182.70   $182.70  
  Purchase #2 $34.63   10.473%   $38.2568   $38.26   $38.25   $38.30  
  Purchase #3 $214.43   12.824%   $241.9285   $241.93   $241.95   $241.90  
  Purchase #4 $48.53   13.777%   $55.216   $55.22   $55.20   $55.20  
  Purchase #5 $56.40   8.132%   $60.9864   $60.99   $61.00   $61.00  
  Purchase #6 $246.84   5.469%   $260.3397   $260.34   $260.35   $260.30  
  Purchase #7 $174.41   12.699%   $196.5583   $196.56   $196.55   $196.60  
  7 purchase totals = $938.66       $1,035.9696   $1,035.98   $1,036.00   $1,036.00