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 $87.71   7.655%   $94.4242   $94.42   $94.40   $94.40  
  Purchase #2 $197.48   13.461%   $224.0628   $224.06   $224.05   $224.10  
  Purchase #3 $48.46   12.202%   $54.3731   $54.37   $54.35   $54.40  
  Purchase #4 $191.46   12.610%   $215.6031   $215.60   $215.60   $215.60  
  Purchase #5 $180.75   9.242%   $197.4549   $197.45   $197.45   $197.50  
  Purchase #6 $216.58   6.311%   $230.2484   $230.25   $230.25   $230.20  
  Purchase #7 $5.88   3.501%   $6.0859   $6.09   $6.10   $6.10  
  7 purchase totals = $928.32       $1,022.2524   $1,022.24   $1,022.20   $1,022.30