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 $47.46   5.493%   $50.067   $50.07   $50.05   $50.10  
  Purchase #2 $233.34   7.704%   $251.3165   $251.32   $251.30   $251.30  
  Purchase #3 $101.94   12.293%   $114.4715   $114.47   $114.45   $114.50  
  Purchase #4 $170.83   3.609%   $176.9953   $177.00   $177.00   $177.00  
  Purchase #5 $136.61   6.557%   $145.5675   $145.57   $145.55   $145.60  
  Purchase #6 $104.42   6.203%   $110.8972   $110.90   $110.90   $110.90  
  Purchase #7 $95.93   7.365%   $102.9952   $103.00   $103.00   $103.00  
  7 purchase totals = $890.53       $952.3102   $952.33   $952.25   $952.40