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 $162.32   8.564%   $176.2211   $176.22   $176.20   $176.20  
  Purchase #2 $216.39   3.358%   $223.6564   $223.66   $223.65   $223.70  
  Purchase #3 $187.75   9.629%   $205.8284   $205.83   $205.85   $205.80  
  Purchase #4 $78.73   3.106%   $81.1754   $81.18   $81.20   $81.20  
  Purchase #5 $248.33   5.752%   $262.6139   $262.61   $262.60   $262.60  
  Purchase #6 $114.91   13.776%   $130.74   $130.74   $130.75   $130.70  
  Purchase #7 $54.77   10.473%   $60.5061   $60.51   $60.50   $60.50  
  7 purchase totals = $1,063.20       $1,140.7413   $1,140.75   $1,140.75   $1,140.70