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 $60.51   3.568%   $62.669   $62.67   $62.65   $62.70  
  Purchase #2 $164.60   10.687%   $182.1908   $182.19   $182.20   $182.20  
  Purchase #3 $144.97   13.425%   $164.4322   $164.43   $164.45   $164.40  
  Purchase #4 $230.86   13.811%   $262.7441   $262.74   $262.75   $262.70  
  Purchase #5 $226.83   10.669%   $251.0305   $251.03   $251.05   $251.00  
  Purchase #6 $42.61   13.532%   $48.376   $48.38   $48.40   $48.40  
  Purchase #7 $31.63   3.326%   $32.682   $32.68   $32.70   $32.70  
  7 purchase totals = $902.01       $1,004.1246   $1,004.12   $1,004.20   $1,004.10