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 $53.49   9.170%   $58.395   $58.40   $58.40   $58.40  
  Purchase #2 $184.66   11.493%   $205.883   $205.88   $205.90   $205.90  
  Purchase #3 $43.63   3.728%   $45.2565   $45.26   $45.25   $45.30  
  Purchase #4 $216.94   3.356%   $224.2205   $224.22   $224.20   $224.20  
  Purchase #5 $44.69   9.641%   $48.9986   $49.00   $49.00   $49.00  
  Purchase #6 $41.41   7.596%   $44.5555   $44.56   $44.55   $44.60  
  Purchase #7 $141.38   9.588%   $154.9355   $154.94   $154.95   $154.90  
  7 purchase totals = $726.20       $782.2446   $782.26   $782.25   $782.30