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 $42.61   8.423%   $46.199   $46.20   $46.20   $46.20  
  Purchase #2 $212.62   13.581%   $241.4959   $241.50   $241.50   $241.50  
  Purchase #3 $5.81   5.844%   $6.1495   $6.15   $6.15   $6.10  
  Purchase #4 $102.63   3.510%   $106.2323   $106.23   $106.25   $106.20  
  Purchase #5 $111.68   3.187%   $115.2392   $115.24   $115.25   $115.20  
  Purchase #6 $123.44   6.691%   $131.6994   $131.70   $131.70   $131.70  
  Purchase #7 $58.81   3.867%   $61.0842   $61.08   $61.10   $61.10  
  7 purchase totals = $657.60       $708.0995   $708.10   $708.15   $708.00