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 $105.88   8.309%   $114.6776   $114.68   $114.70   $114.70  
  Purchase #2 $77.58   10.320%   $85.5863   $85.59   $85.60   $85.60  
  Purchase #3 $166.49   6.855%   $177.9029   $177.90   $177.90   $177.90  
  Purchase #4 $109.60   4.143%   $114.1407   $114.14   $114.15   $114.10  
  Purchase #5 $232.29   13.314%   $263.2171   $263.22   $263.20   $263.20  
  Purchase #6 $213.73   3.518%   $221.249   $221.25   $221.25   $221.20  
  Purchase #7 $170.85   10.611%   $188.9789   $188.98   $189.00   $189.00  
  7 purchase totals = $1,076.42       $1,165.7525   $1,165.76   $1,165.80   $1,165.70