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 $235.51   11.316%   $262.1603   $262.16   $262.15   $262.20  
  Purchase #2 $142.68   9.569%   $156.333   $156.33   $156.35   $156.30  
  Purchase #3 $87.33   8.630%   $94.8666   $94.87   $94.85   $94.90  
  Purchase #4 $27.82   9.284%   $30.4028   $30.40   $30.40   $30.40  
  Purchase #5 $245.49   5.196%   $258.2457   $258.25   $258.25   $258.20  
  Purchase #6 $54.27   6.158%   $57.6119   $57.61   $57.60   $57.60  
  Purchase #7 $163.96   11.419%   $182.6826   $182.68   $182.70   $182.70  
  7 purchase totals = $957.06       $1,042.3029   $1,042.30   $1,042.30   $1,042.30