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 $201.73   11.156%   $224.235   $224.24   $224.25   $224.20  
  Purchase #2 $186.73   13.124%   $211.2364   $211.24   $211.25   $211.20  
  Purchase #3 $168.40   11.317%   $187.4578   $187.46   $187.45   $187.50  
  Purchase #4 $106.41   7.801%   $114.711   $114.71   $114.70   $114.70  
  Purchase #5 $132.54   6.329%   $140.9285   $140.93   $140.95   $140.90  
  Purchase #6 $59.40   8.697%   $64.566   $64.57   $64.55   $64.60  
  Purchase #7 $56.98   12.148%   $63.9019   $63.90   $63.90   $63.90  
  7 purchase totals = $912.19       $1,007.0366   $1,007.05   $1,007.05   $1,007.00