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 $23.63   8.275%   $25.5854   $25.59   $25.60   $25.60  
  Purchase #2 $114.82   7.166%   $123.048   $123.05   $123.05   $123.00  
  Purchase #3 $203.25   5.142%   $213.7011   $213.70   $213.70   $213.70  
  Purchase #4 $24.68   5.444%   $26.0236   $26.02   $26.00   $26.00  
  Purchase #5 $61.64   11.142%   $68.5079   $68.51   $68.50   $68.50  
  Purchase #6 $16.75   8.729%   $18.2121   $18.21   $18.20   $18.20  
  Purchase #7 $240.50   12.295%   $270.0695   $270.07   $270.05   $270.10  
  7 purchase totals = $685.27       $745.1476   $745.15   $745.10   $745.10