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 $227.89   5.778%   $241.0575   $241.06   $241.05   $241.10  
  Purchase #2 $60.42   4.352%   $63.0495   $63.05   $63.05   $63.00  
  Purchase #3 $82.93   13.528%   $94.1488   $94.15   $94.15   $94.10  
  Purchase #4 $168.29   8.821%   $183.1349   $183.13   $183.15   $183.10  
  Purchase #5 $130.25   3.353%   $134.6173   $134.62   $134.60   $134.60  
  Purchase #6 $232.44   12.754%   $262.0854   $262.09   $262.10   $262.10  
  Purchase #7 $110.42   7.232%   $118.4056   $118.41   $118.40   $118.40  
  7 purchase totals = $1,012.64       $1,096.4990   $1,096.51   $1,096.50   $1,096.40