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 $196.25   5.679%   $207.395   $207.40   $207.40   $207.40  
  Purchase #2 $213.47   6.752%   $227.8835   $227.88   $227.90   $227.90  
  Purchase #3 $26.89   9.431%   $29.426   $29.43   $29.45   $29.40  
  Purchase #4 $231.96   13.733%   $263.8151   $263.82   $263.80   $263.80  
  Purchase #5 $51.96   7.109%   $55.6538   $55.65   $55.65   $55.70  
  Purchase #6 $104.27   9.636%   $114.3175   $114.32   $114.30   $114.30  
  Purchase #7 $154.88   4.155%   $161.3153   $161.32   $161.30   $161.30  
  7 purchase totals = $979.68       $1,059.8062   $1,059.82   $1,059.80   $1,059.80