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 $108.67   7.436%   $116.7507   $116.75   $116.75   $116.80  
  Purchase #2 $236.61   6.691%   $252.4416   $252.44   $252.45   $252.40  
  Purchase #3 $156.70   7.677%   $168.7299   $168.73   $168.75   $168.70  
  Purchase #4 $167.93   5.221%   $176.6976   $176.70   $176.70   $176.70  
  Purchase #5 $63.95   6.246%   $67.9443   $67.94   $67.95   $67.90  
  Purchase #6 $185.53   5.433%   $195.6098   $195.61   $195.60   $195.60  
  Purchase #7 $244.40   7.580%   $262.9255   $262.93   $262.95   $262.90  
  7 purchase totals = $1,163.79       $1,241.0994   $1,241.10   $1,241.15   $1,241.00