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 $114.71   10.635%   $126.9094   $126.91   $126.90   $126.90  
  Purchase #2 $142.74   8.607%   $155.0256   $155.03   $155.05   $155.00  
  Purchase #3 $117.32   3.211%   $121.0871   $121.09   $121.10   $121.10  
  Purchase #4 $186.43   11.446%   $207.7688   $207.77   $207.75   $207.80  
  Purchase #5 $224.77   6.483%   $239.3418   $239.34   $239.35   $239.30  
  Purchase #6 $192.85   12.761%   $217.4596   $217.46   $217.45   $217.50  
  Purchase #7 $52.89   10.552%   $58.471   $58.47   $58.45   $58.50  
  7 purchase totals = $1,031.71       $1,126.0633   $1,126.07   $1,126.05   $1,126.10