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 $214.99   5.661%   $227.1606   $227.16   $227.15   $227.20  
  Purchase #2 $206.77   4.448%   $215.9671   $215.97   $215.95   $216.00  
  Purchase #3 $159.25   10.481%   $175.941   $175.94   $175.95   $175.90  
  Purchase #4 $155.33   8.170%   $168.0205   $168.02   $168.00   $168.00  
  Purchase #5 $214.70   8.832%   $233.6623   $233.66   $233.65   $233.70  
  Purchase #6 $129.97   7.514%   $139.7359   $139.74   $139.75   $139.70  
  Purchase #7 $144.47   9.144%   $157.6803   $157.68   $157.70   $157.70  
  7 purchase totals = $1,225.48       $1,318.1677   $1,318.17   $1,318.15   $1,318.20