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 $56.78   9.313%   $62.0679   $62.07   $62.05   $62.10  
  Purchase #2 $199.25   5.667%   $210.5415   $210.54   $210.55   $210.50  
  Purchase #3 $124.81   11.854%   $139.605   $139.61   $139.60   $139.60  
  Purchase #4 $238.32   8.787%   $259.2612   $259.26   $259.25   $259.30  
  Purchase #5 $24.55   9.144%   $26.7949   $26.79   $26.80   $26.80  
  Purchase #6 $192.85   6.652%   $205.6784   $205.68   $205.70   $205.70  
  Purchase #7 $142.81   8.609%   $155.1045   $155.10   $155.10   $155.10  
  7 purchase totals = $979.37       $1,059.0534   $1,059.05   $1,059.05   $1,059.10