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 $215.88   7.739%   $232.587   $232.59   $232.60   $232.60  
  Purchase #2 $102.28   3.235%   $105.5888   $105.59   $105.60   $105.60  
  Purchase #3 $202.91   9.260%   $221.6995   $221.70   $221.70   $221.70  
  Purchase #4 $217.37   6.771%   $232.0881   $232.09   $232.10   $232.10  
  Purchase #5 $148.28   4.188%   $154.49   $154.49   $154.50   $154.50  
  Purchase #6 $231.80   11.822%   $259.2034   $259.20   $259.20   $259.20  
  Purchase #7 $235.26   11.123%   $261.428   $261.43   $261.45   $261.40  
  7 purchase totals = $1,353.78       $1,467.0848   $1,467.09   $1,467.15   $1,467.10