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 $232.46   6.753%   $248.158   $248.16   $248.15   $248.20  
  Purchase #2 $56.73   7.709%   $61.1033   $61.10   $61.10   $61.10  
  Purchase #3 $31.62   3.615%   $32.7631   $32.76   $32.75   $32.80  
  Purchase #4 $234.82   11.178%   $261.0682   $261.07   $261.05   $261.10  
  Purchase #5 $215.71   13.138%   $244.05   $244.05   $244.05   $244.10  
  Purchase #6 $194.39   12.102%   $217.9151   $217.92   $217.90   $217.90  
  Purchase #7 $65.55   5.313%   $69.0327   $69.03   $69.05   $69.00  
  7 purchase totals = $1,031.28       $1,134.0904   $1,134.09   $1,134.05   $1,134.20