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 $175.73   3.676%   $182.1898   $182.19   $182.20   $182.20  
  Purchase #2 $207.83   11.706%   $232.1586   $232.16   $232.15   $232.20  
  Purchase #3 $125.85   6.284%   $133.7584   $133.76   $133.75   $133.80  
  Purchase #4 $54.55   4.790%   $57.1629   $57.16   $57.15   $57.20  
  Purchase #5 $77.94   6.255%   $82.8151   $82.82   $82.80   $82.80  
  Purchase #6 $130.87   5.194%   $137.6674   $137.67   $137.65   $137.70  
  Purchase #7 $118.52   4.827%   $124.241   $124.24   $124.25   $124.20  
  7 purchase totals = $891.29       $949.9932   $950.00   $949.95   $950.10