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 $44.54   8.231%   $48.2061   $48.21   $48.20   $48.20  
  Purchase #2 $237.40   10.442%   $262.1893   $262.19   $262.20   $262.20  
  Purchase #3 $102.43   12.772%   $115.5124   $115.51   $115.50   $115.50  
  Purchase #4 $185.86   3.569%   $192.4933   $192.49   $192.50   $192.50  
  Purchase #5 $115.38   10.568%   $127.5734   $127.57   $127.55   $127.60  
  Purchase #6 $248.45   9.357%   $271.6975   $271.70   $271.70   $271.70  
  Purchase #7 $108.59   7.178%   $116.3846   $116.38   $116.40   $116.40  
  7 purchase totals = $1,042.65       $1,134.0566   $1,134.05   $1,134.05   $1,134.10