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 $90.80   3.482%   $93.9617   $93.96   $93.95   $94.00  
  Purchase #2 $198.51   7.830%   $214.0533   $214.05   $214.05   $214.10  
  Purchase #3 $190.81   7.298%   $204.7353   $204.74   $204.75   $204.70  
  Purchase #4 $180.51   3.436%   $186.7123   $186.71   $186.70   $186.70  
  Purchase #5 $163.78   9.378%   $179.1393   $179.14   $179.15   $179.10  
  Purchase #6 $55.43   3.622%   $57.4377   $57.44   $57.45   $57.40  
  Purchase #7 $236.25   11.553%   $263.544   $263.54   $263.55   $263.50  
  7 purchase totals = $1,116.09       $1,199.5836   $1,199.58   $1,199.60   $1,199.50