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 $42.97   11.595%   $47.9524   $47.95   $47.95   $48.00  
  Purchase #2 $152.98   7.757%   $164.8467   $164.85   $164.85   $164.80  
  Purchase #3 $64.34   8.664%   $69.9144   $69.91   $69.90   $69.90  
  Purchase #4 $165.59   3.549%   $171.4668   $171.47   $171.45   $171.50  
  Purchase #5 $104.93   9.834%   $115.2488   $115.25   $115.25   $115.20  
  Purchase #6 $244.78   12.595%   $275.61   $275.61   $275.60   $275.60  
  Purchase #7 $183.59   8.851%   $199.8396   $199.84   $199.85   $199.80  
  7 purchase totals = $959.18       $1,044.8787   $1,044.88   $1,044.85   $1,044.80