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 $224.71   9.495%   $246.0462   $246.05   $246.05   $246.00  
  Purchase #2 $207.60   8.837%   $225.9456   $225.95   $225.95   $225.90  
  Purchase #3 $63.56   12.462%   $71.4808   $71.48   $71.50   $71.50  
  Purchase #4 $129.36   8.805%   $140.7501   $140.75   $140.75   $140.80  
  Purchase #5 $86.63   11.157%   $96.2953   $96.30   $96.30   $96.30  
  Purchase #6 $85.49   12.255%   $95.9668   $95.97   $95.95   $96.00  
  Purchase #7 $20.27   6.748%   $21.6378   $21.64   $21.65   $21.60  
  7 purchase totals = $817.62       $898.1226   $898.14   $898.15   $898.10