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 $213.41   10.649%   $236.136   $236.14   $236.15   $236.10  
  Purchase #2 $186.70   8.681%   $202.9074   $202.91   $202.90   $202.90  
  Purchase #3 $115.42   6.110%   $122.4722   $122.47   $122.45   $122.50  
  Purchase #4 $72.68   10.615%   $80.395   $80.40   $80.40   $80.40  
  Purchase #5 $67.37   12.369%   $75.703   $75.70   $75.70   $75.70  
  Purchase #6 $166.92   4.257%   $174.0258   $174.03   $174.05   $174.00  
  Purchase #7 $167.58   10.327%   $184.886   $184.89   $184.90   $184.90  
  7 purchase totals = $990.08       $1,076.5254   $1,076.54   $1,076.55   $1,076.50