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 $172.35   11.832%   $192.7425   $192.74   $192.75   $192.70  
  Purchase #2 $195.67   3.522%   $202.5615   $202.56   $202.55   $202.60  
  Purchase #3 $179.75   11.858%   $201.0648   $201.06   $201.05   $201.10  
  Purchase #4 $226.34   6.667%   $241.4301   $241.43   $241.45   $241.40  
  Purchase #5 $238.28   6.136%   $252.9009   $252.90   $252.90   $252.90  
  Purchase #6 $177.46   9.231%   $193.8413   $193.84   $193.85   $193.80  
  Purchase #7 $76.76   8.451%   $83.247   $83.25   $83.25   $83.20  
  7 purchase totals = $1,266.61       $1,367.7881   $1,367.78   $1,367.80   $1,367.70