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 $41.68   10.480%   $46.0481   $46.05   $46.05   $46.00  
  Purchase #2 $176.63   5.303%   $185.9967   $186.00   $186.00   $186.00  
  Purchase #3 $25.60   7.267%   $27.4604   $27.46   $27.45   $27.50  
  Purchase #4 $100.47   13.631%   $114.1651   $114.17   $114.15   $114.20  
  Purchase #5 $56.36   6.855%   $60.2235   $60.22   $60.20   $60.20  
  Purchase #6 $164.62   13.289%   $186.4964   $186.50   $186.50   $186.50  
  Purchase #7 $24.94   9.655%   $27.348   $27.35   $27.35   $27.30  
  7 purchase totals = $590.30       $647.7382   $647.75   $647.70   $647.70