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 $214.70   3.523%   $222.2639   $222.26   $222.25   $222.30  
  Purchase #2 $85.94   7.817%   $92.6579   $92.66   $92.65   $92.70  
  Purchase #3 $201.77   7.871%   $217.6513   $217.65   $217.65   $217.70  
  Purchase #4 $118.98   11.488%   $132.6484   $132.65   $132.65   $132.60  
  Purchase #5 $136.99   6.293%   $145.6108   $145.61   $145.60   $145.60  
  Purchase #6 $57.61   6.105%   $61.1271   $61.13   $61.15   $61.10  
  Purchase #7 $54.69   9.765%   $60.0305   $60.03   $60.05   $60.00  
  7 purchase totals = $870.68       $931.9899   $931.99   $932.00   $932.00