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 $214.90   5.554%   $226.8355   $226.84   $226.85   $226.80  
  Purchase #2 $33.93   9.826%   $37.264   $37.26   $37.25   $37.30  
  Purchase #3 $106.32   3.161%   $109.6808   $109.68   $109.70   $109.70  
  Purchase #4 $195.35   9.747%   $214.3908   $214.39   $214.40   $214.40  
  Purchase #5 $72.81   5.355%   $76.709   $76.71   $76.70   $76.70  
  Purchase #6 $126.27   5.423%   $133.1176   $133.12   $133.10   $133.10  
  Purchase #7 $108.71   5.746%   $114.9565   $114.96   $114.95   $115.00  
  7 purchase totals = $858.29       $912.9542   $912.96   $912.95   $913.00