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 $119.50   4.695%   $125.1105   $125.11   $125.10   $125.10  
  Purchase #2 $166.49   7.669%   $179.2581   $179.26   $179.25   $179.30  
  Purchase #3 $48.27   4.138%   $50.2674   $50.27   $50.25   $50.30  
  Purchase #4 $243.65   6.542%   $259.5896   $259.59   $259.60   $259.60  
  Purchase #5 $230.46   11.435%   $256.8131   $256.81   $256.80   $256.80  
  Purchase #6 $25.48   8.765%   $27.7133   $27.71   $27.70   $27.70  
  Purchase #7 $111.39   7.439%   $119.6763   $119.68   $119.70   $119.70  
  7 purchase totals = $945.24       $1,018.4283   $1,018.43   $1,018.40   $1,018.50