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 $196.31   4.423%   $204.9928   $204.99   $205.00   $205.00  
  Purchase #2 $134.49   12.478%   $151.2717   $151.27   $151.25   $151.30  
  Purchase #3 $189.30   4.398%   $197.6254   $197.63   $197.65   $197.60  
  Purchase #4 $49.79   11.162%   $55.3476   $55.35   $55.35   $55.30  
  Purchase #5 $213.78   5.592%   $225.7346   $225.73   $225.75   $225.70  
  Purchase #6 $153.34   3.282%   $158.3726   $158.37   $158.35   $158.40  
  Purchase #7 $60.91   13.286%   $69.0025   $69.00   $69.00   $69.00  
  7 purchase totals = $997.92       $1,062.3472   $1,062.34   $1,062.35   $1,062.30