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 $119.32   5.122%   $125.4316   $125.43   $125.45   $125.40  
  Purchase #2 $76.81   5.495%   $81.0307   $81.03   $81.05   $81.00  
  Purchase #3 $56.49   7.320%   $60.6251   $60.63   $60.65   $60.60  
  Purchase #4 $244.70   6.444%   $260.4685   $260.47   $260.45   $260.50  
  Purchase #5 $211.61   12.216%   $237.4603   $237.46   $237.45   $237.50  
  Purchase #6 $163.51   12.169%   $183.4075   $183.41   $183.40   $183.40  
  Purchase #7 $221.98   4.575%   $232.1356   $232.14   $232.15   $232.10  
  7 purchase totals = $1,094.42       $1,180.5593   $1,180.57   $1,180.60   $1,180.50