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 $91.66   5.243%   $96.4657   $96.47   $96.45   $96.50  
  Purchase #2 $249.56   4.435%   $260.628   $260.63   $260.65   $260.60  
  Purchase #3 $143.92   13.307%   $163.0714   $163.07   $163.05   $163.10  
  Purchase #4 $247.63   8.372%   $268.3616   $268.36   $268.35   $268.40  
  Purchase #5 $42.54   7.426%   $45.699   $45.70   $45.70   $45.70  
  Purchase #6 $244.45   5.409%   $257.6723   $257.67   $257.65   $257.70  
  Purchase #7 $131.47   9.819%   $144.379   $144.38   $144.40   $144.40  
  7 purchase totals = $1,151.23       $1,236.2770   $1,236.28   $1,236.25   $1,236.40