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 $24.42   7.332%   $26.2105   $26.21   $26.20   $26.20  
  Purchase #2 $35.85   5.326%   $37.7594   $37.76   $37.75   $37.80  
  Purchase #3 $158.28   11.584%   $176.6152   $176.62   $176.60   $176.60  
  Purchase #4 $153.57   12.414%   $172.6342   $172.63   $172.65   $172.60  
  Purchase #5 $36.83   11.246%   $40.9719   $40.97   $40.95   $41.00  
  Purchase #6 $114.36   4.395%   $119.3861   $119.39   $119.40   $119.40  
  Purchase #7 $180.62   11.639%   $201.6424   $201.64   $201.65   $201.60  
  7 purchase totals = $703.93       $775.2197   $775.22   $775.20   $775.20