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 $175.66   3.771%   $182.2841   $182.28   $182.30   $182.30  
  Purchase #2 $120.94   8.644%   $131.3941   $131.39   $131.40   $131.40  
  Purchase #3 $188.81   4.839%   $197.9465   $197.95   $197.95   $197.90  
  Purchase #4 $146.83   5.764%   $155.2933   $155.29   $155.30   $155.30  
  Purchase #5 $73.83   3.107%   $76.1239   $76.12   $76.10   $76.10  
  Purchase #6 $153.29   8.398%   $166.1633   $166.16   $166.15   $166.20  
  Purchase #7 $236.29   7.509%   $254.033   $254.03   $254.05   $254.00  
  7 purchase totals = $1,095.65       $1,163.2382   $1,163.22   $1,163.25   $1,163.20