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 $216.99   5.721%   $229.404   $229.40   $229.40   $229.40  
  Purchase #2 $229.46   10.532%   $253.6267   $253.63   $253.65   $253.60  
  Purchase #3 $65.76   4.260%   $68.5614   $68.56   $68.55   $68.60  
  Purchase #4 $241.28   5.455%   $254.4418   $254.44   $254.45   $254.40  
  Purchase #5 $77.89   8.255%   $84.3198   $84.32   $84.30   $84.30  
  Purchase #6 $135.77   5.372%   $143.0636   $143.06   $143.05   $143.10  
  Purchase #7 $164.84   3.420%   $170.4775   $170.48   $170.50   $170.50  
  7 purchase totals = $1,131.99       $1,203.8948   $1,203.89   $1,203.90   $1,203.90