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 $195.93   6.135%   $207.9503   $207.95   $207.95   $208.00  
  Purchase #2 $211.61   3.748%   $219.5411   $219.54   $219.55   $219.50  
  Purchase #3 $163.61   12.146%   $183.4821   $183.48   $183.50   $183.50  
  Purchase #4 $97.50   13.328%   $110.4948   $110.49   $110.50   $110.50  
  Purchase #5 $206.61   8.194%   $223.5396   $223.54   $223.55   $223.50  
  Purchase #6 $121.63   13.724%   $138.3225   $138.32   $138.30   $138.30  
  Purchase #7 $26.99   11.109%   $29.9883   $29.99   $30.00   $30.00  
  7 purchase totals = $1,023.88       $1,113.3187   $1,113.31   $1,113.35   $1,113.30