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 $209.47   8.149%   $226.5397   $226.54   $226.55   $226.50  
  Purchase #2 $11.94   9.434%   $13.0664   $13.07   $13.05   $13.10  
  Purchase #3 $214.35   10.393%   $236.6274   $236.63   $236.65   $236.60  
  Purchase #4 $173.87   4.164%   $181.1099   $181.11   $181.10   $181.10  
  Purchase #5 $141.75   6.569%   $151.0616   $151.06   $151.05   $151.10  
  Purchase #6 $199.56   6.716%   $212.9624   $212.96   $212.95   $213.00  
  Purchase #7 $186.70   4.553%   $195.2005   $195.20   $195.20   $195.20  
  7 purchase totals = $1,137.64       $1,216.5679   $1,216.57   $1,216.55   $1,216.60