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 $59.63   4.479%   $62.3008   $62.30   $62.30   $62.30  
  Purchase #2 $229.63   13.728%   $261.1536   $261.15   $261.15   $261.20  
  Purchase #3 $104.56   9.822%   $114.8299   $114.83   $114.85   $114.80  
  Purchase #4 $40.84   11.107%   $45.3761   $45.38   $45.40   $45.40  
  Purchase #5 $168.38   6.113%   $178.6731   $178.67   $178.65   $178.70  
  Purchase #6 $207.64   3.596%   $215.1067   $215.11   $215.10   $215.10  
  Purchase #7 $240.30   12.357%   $269.9939   $269.99   $270.00   $270.00  
  7 purchase totals = $1,050.98       $1,147.4341   $1,147.43   $1,147.45   $1,147.50