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 $77.28   11.660%   $86.2908   $86.29   $86.30   $86.30  
  Purchase #2 $236.57   10.671%   $261.8144   $261.81   $261.80   $261.80  
  Purchase #3 $249.85   13.734%   $284.1644   $284.16   $284.15   $284.20  
  Purchase #4 $144.27   12.426%   $162.197   $162.20   $162.20   $162.20  
  Purchase #5 $118.95   7.576%   $127.9617   $127.96   $127.95   $128.00  
  Purchase #6 $168.69   11.431%   $187.973   $187.97   $187.95   $188.00  
  Purchase #7 $226.61   10.255%   $249.8489   $249.85   $249.85   $249.80  
  7 purchase totals = $1,222.22       $1,360.2502   $1,360.24   $1,360.20   $1,360.30