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 $216.56   9.697%   $237.5598   $237.56   $237.55   $237.60  
  Purchase #2 $73.28   3.592%   $75.9122   $75.91   $75.90   $75.90  
  Purchase #3 $207.58   9.515%   $227.3312   $227.33   $227.35   $227.30  
  Purchase #4 $241.33   8.533%   $261.9227   $261.92   $261.90   $261.90  
  Purchase #5 $116.79   7.153%   $125.144   $125.14   $125.15   $125.10  
  Purchase #6 $168.37   5.663%   $177.9048   $177.90   $177.90   $177.90  
  Purchase #7 $241.33   9.287%   $263.7423   $263.74   $263.75   $263.70  
  7 purchase totals = $1,265.24       $1,369.5170   $1,369.50   $1,369.50   $1,369.40