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 $114.69   10.406%   $126.6246   $126.62   $126.60   $126.60  
  Purchase #2 $106.74   8.411%   $115.7179   $115.72   $115.70   $115.70  
  Purchase #3 $54.86   3.798%   $56.9436   $56.94   $56.95   $56.90  
  Purchase #4 $206.83   10.281%   $228.0942   $228.09   $228.10   $228.10  
  Purchase #5 $194.53   12.308%   $218.4728   $218.47   $218.45   $218.50  
  Purchase #6 $143.70   5.655%   $151.8262   $151.83   $151.85   $151.80  
  Purchase #7 $147.88   9.635%   $162.1282   $162.13   $162.15   $162.10  
  7 purchase totals = $969.23       $1,059.8075   $1,059.80   $1,059.80   $1,059.70