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 $90.26   6.358%   $95.9987   $96.00   $96.00   $96.00  
  Purchase #2 $221.35   9.545%   $242.4779   $242.48   $242.50   $242.50  
  Purchase #3 $218.94   8.110%   $236.696   $236.70   $236.70   $236.70  
  Purchase #4 $204.26   8.533%   $221.6895   $221.69   $221.70   $221.70  
  Purchase #5 $53.58   5.196%   $56.364   $56.36   $56.35   $56.40  
  Purchase #6 $176.93   13.603%   $200.9978   $201.00   $201.00   $201.00  
  Purchase #7 $49.27   9.307%   $53.8556   $53.86   $53.85   $53.90  
  7 purchase totals = $1,014.59       $1,108.0795   $1,108.09   $1,108.10   $1,108.20