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 $116.93   7.423%   $125.6097   $125.61   $125.60   $125.60  
  Purchase #2 $81.77   12.698%   $92.1532   $92.15   $92.15   $92.20  
  Purchase #3 $168.71   7.383%   $181.1659   $181.17   $181.15   $181.20  
  Purchase #4 $99.63   4.685%   $104.2977   $104.30   $104.30   $104.30  
  Purchase #5 $194.43   10.720%   $215.2729   $215.27   $215.25   $215.30  
  Purchase #6 $240.83   13.537%   $273.4312   $273.43   $273.45   $273.40  
  Purchase #7 $241.63   5.289%   $254.4098   $254.41   $254.40   $254.40  
  7 purchase totals = $1,143.93       $1,246.3404   $1,246.34   $1,246.30   $1,246.40