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 $58.43   6.503%   $62.2297   $62.23   $62.25   $62.20  
  Purchase #2 $144.25   8.632%   $156.7017   $156.70   $156.70   $156.70  
  Purchase #3 $113.53   7.847%   $122.4387   $122.44   $122.45   $122.40  
  Purchase #4 $21.78   4.233%   $22.7019   $22.70   $22.70   $22.70  
  Purchase #5 $120.44   12.813%   $135.872   $135.87   $135.85   $135.90  
  Purchase #6 $190.32   5.271%   $200.3518   $200.35   $200.35   $200.40  
  Purchase #7 $245.49   7.792%   $264.6186   $264.62   $264.60   $264.60  
  7 purchase totals = $894.24       $964.9144   $964.91   $964.90   $964.90