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 $212.80   6.528%   $226.6916   $226.69   $226.70   $226.70  
  Purchase #2 $48.67   8.142%   $52.6327   $52.63   $52.65   $52.60  
  Purchase #3 $14.89   12.863%   $16.8053   $16.81   $16.80   $16.80  
  Purchase #4 $149.83   5.688%   $158.3523   $158.35   $158.35   $158.40  
  Purchase #5 $201.93   12.131%   $226.4261   $226.43   $226.45   $226.40  
  Purchase #6 $58.76   11.660%   $65.6114   $65.61   $65.60   $65.60  
  Purchase #7 $207.25   4.567%   $216.7151   $216.72   $216.70   $216.70  
  7 purchase totals = $894.13       $963.2345   $963.24   $963.25   $963.20