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 $224.36   11.690%   $250.5877   $250.59   $250.60   $250.60  
  Purchase #2 $202.39   5.424%   $213.3676   $213.37   $213.35   $213.40  
  Purchase #3 $44.38   3.783%   $46.0589   $46.06   $46.05   $46.10  
  Purchase #4 $235.85   7.325%   $253.126   $253.13   $253.15   $253.10  
  Purchase #5 $225.26   3.436%   $232.9999   $233.00   $233.00   $233.00  
  Purchase #6 $192.43   8.585%   $208.9501   $208.95   $208.95   $209.00  
  Purchase #7 $249.63   6.306%   $265.3717   $265.37   $265.35   $265.40  
  7 purchase totals = $1,374.30       $1,470.4619   $1,470.47   $1,470.45   $1,470.60