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 $232.81   13.863%   $265.0845   $265.08   $265.10   $265.10  
  Purchase #2 $238.86   11.584%   $266.5295   $266.53   $266.55   $266.50  
  Purchase #3 $104.58   9.159%   $114.1585   $114.16   $114.15   $114.20  
  Purchase #4 $43.68   5.623%   $46.1361   $46.14   $46.15   $46.10  
  Purchase #5 $249.92   7.800%   $269.4138   $269.41   $269.40   $269.40  
  Purchase #6 $63.55   11.572%   $70.904   $70.90   $70.90   $70.90  
  Purchase #7 $89.51   5.485%   $94.4196   $94.42   $94.40   $94.40  
  7 purchase totals = $1,022.91       $1,126.6460   $1,126.64   $1,126.65   $1,126.60