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 $62.85   3.549%   $65.0805   $65.08   $65.10   $65.10  
  Purchase #2 $179.89   6.817%   $192.1531   $192.15   $192.15   $192.20  
  Purchase #3 $29.88   7.705%   $32.1823   $32.18   $32.20   $32.20  
  Purchase #4 $218.91   8.146%   $236.7424   $236.74   $236.75   $236.70  
  Purchase #5 $221.45   4.167%   $230.6778   $230.68   $230.70   $230.70  
  Purchase #6 $27.82   8.785%   $30.264   $30.26   $30.25   $30.30  
  Purchase #7 $208.58   7.304%   $223.8147   $223.81   $223.80   $223.80  
  7 purchase totals = $949.38       $1,010.9148   $1,010.90   $1,010.95   $1,011.00