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 $168.86   9.851%   $185.4944   $185.49   $185.50   $185.50  
  Purchase #2 $232.90   12.195%   $261.3022   $261.30   $261.30   $261.30  
  Purchase #3 $232.98   12.487%   $262.0722   $262.07   $262.05   $262.10  
  Purchase #4 $77.36   4.398%   $80.7623   $80.76   $80.75   $80.80  
  Purchase #5 $221.44   3.801%   $229.8569   $229.86   $229.85   $229.90  
  Purchase #6 $182.93   12.518%   $205.8292   $205.83   $205.85   $205.80  
  Purchase #7 $218.90   10.549%   $241.9918   $241.99   $242.00   $242.00  
  7 purchase totals = $1,335.37       $1,467.3090   $1,467.30   $1,467.30   $1,467.40