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 $203.66   5.522%   $214.9061   $214.91   $214.90   $214.90  
  Purchase #2 $211.85   5.124%   $222.7052   $222.71   $222.70   $222.70  
  Purchase #3 $87.59   4.167%   $91.2399   $91.24   $91.25   $91.20  
  Purchase #4 $94.70   4.484%   $98.9463   $98.95   $98.95   $98.90  
  Purchase #5 $173.26   10.547%   $191.5337   $191.53   $191.55   $191.50  
  Purchase #6 $58.88   13.264%   $66.6898   $66.69   $66.70   $66.70  
  Purchase #7 $131.68   3.448%   $136.2203   $136.22   $136.20   $136.20  
  7 purchase totals = $961.62       $1,022.2413   $1,022.25   $1,022.25   $1,022.10