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 $82.59   11.330%   $91.9474   $91.95   $91.95   $91.90  
  Purchase #2 $239.63   8.281%   $259.4738   $259.47   $259.45   $259.50  
  Purchase #3 $160.63   9.701%   $176.2127   $176.21   $176.20   $176.20  
  Purchase #4 $204.45   10.874%   $226.6819   $226.68   $226.70   $226.70  
  Purchase #5 $106.53   6.393%   $113.3405   $113.34   $113.35   $113.30  
  Purchase #6 $126.76   11.459%   $141.2854   $141.29   $141.30   $141.30  
  Purchase #7 $152.75   3.574%   $158.2093   $158.21   $158.20   $158.20  
  7 purchase totals = $1,073.34       $1,167.1510   $1,167.15   $1,167.15   $1,167.10