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 $115.30   3.427%   $119.2513   $119.25   $119.25   $119.30  
  Purchase #2 $95.93   4.757%   $100.4934   $100.49   $100.50   $100.50  
  Purchase #3 $170.36   3.397%   $176.1471   $176.15   $176.15   $176.10  
  Purchase #4 $42.78   7.614%   $46.0373   $46.04   $46.05   $46.00  
  Purchase #5 $183.54   12.203%   $205.9374   $205.94   $205.95   $205.90  
  Purchase #6 $179.98   6.793%   $192.206   $192.21   $192.20   $192.20  
  Purchase #7 $231.76   13.287%   $262.554   $262.55   $262.55   $262.60  
  7 purchase totals = $1,019.65       $1,102.6265   $1,102.63   $1,102.65   $1,102.60