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 $52.56   11.510%   $58.6097   $58.61   $58.60   $58.60  
  Purchase #2 $149.71   6.524%   $159.4771   $159.48   $159.50   $159.50  
  Purchase #3 $198.95   8.641%   $216.1413   $216.14   $216.15   $216.10  
  Purchase #4 $114.96   3.594%   $119.0917   $119.09   $119.10   $119.10  
  Purchase #5 $241.89   10.536%   $267.3755   $267.38   $267.40   $267.40  
  Purchase #6 $237.90   3.138%   $245.3653   $245.37   $245.35   $245.40  
  Purchase #7 $147.25   7.582%   $158.4145   $158.41   $158.40   $158.40  
  7 purchase totals = $1,143.22       $1,224.4751   $1,224.48   $1,224.50   $1,224.50