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 $208.71   13.379%   $236.6333   $236.63   $236.65   $236.60  
  Purchase #2 $87.64   8.483%   $95.0745   $95.07   $95.05   $95.10  
  Purchase #3 $58.84   8.411%   $63.789   $63.79   $63.80   $63.80  
  Purchase #4 $168.91   13.872%   $192.3412   $192.34   $192.35   $192.30  
  Purchase #5 $230.58   5.546%   $243.368   $243.37   $243.35   $243.40  
  Purchase #6 $74.95   12.415%   $84.255   $84.26   $84.25   $84.30  
  Purchase #7 $247.78   8.354%   $268.4795   $268.48   $268.50   $268.50  
  7 purchase totals = $1,077.41       $1,183.9405   $1,183.94   $1,183.95   $1,184.00