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 $192.25   6.788%   $205.2999   $205.30   $205.30   $205.30  
  Purchase #2 $176.61   8.393%   $191.4329   $191.43   $191.45   $191.40  
  Purchase #3 $155.65   3.643%   $161.3203   $161.32   $161.30   $161.30  
  Purchase #4 $9.68   9.669%   $10.616   $10.62   $10.60   $10.60  
  Purchase #5 $198.53   7.526%   $213.4714   $213.47   $213.45   $213.50  
  Purchase #6 $86.90   7.608%   $93.5114   $93.51   $93.50   $93.50  
  Purchase #7 $82.30   5.632%   $86.9351   $86.94   $86.95   $86.90  
  7 purchase totals = $901.92       $962.5870   $962.59   $962.55   $962.50