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 $233.39   12.654%   $262.9232   $262.92   $262.90   $262.90  
  Purchase #2 $194.37   6.629%   $207.2548   $207.25   $207.25   $207.30  
  Purchase #3 $181.97   3.496%   $188.3317   $188.33   $188.35   $188.30  
  Purchase #4 $248.96   11.524%   $277.6502   $277.65   $277.65   $277.70  
  Purchase #5 $100.99   13.342%   $114.4641   $114.46   $114.45   $114.50  
  Purchase #6 $177.44   5.513%   $187.2223   $187.22   $187.20   $187.20  
  Purchase #7 $206.80   10.422%   $228.3527   $228.35   $228.35   $228.40  
  7 purchase totals = $1,343.92       $1,466.1990   $1,466.18   $1,466.15   $1,466.30