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 $224.68   5.436%   $236.8936   $236.89   $236.90   $236.90  
  Purchase #2 $245.75   7.872%   $265.0954   $265.10   $265.10   $265.10  
  Purchase #3 $9.50   8.122%   $10.2716   $10.27   $10.25   $10.30  
  Purchase #4 $94.49   3.757%   $98.04   $98.04   $98.05   $98.00  
  Purchase #5 $160.99   3.161%   $166.0789   $166.08   $166.10   $166.10  
  Purchase #6 $56.95   3.547%   $58.97   $58.97   $58.95   $59.00  
  Purchase #7 $41.83   10.691%   $46.302   $46.30   $46.30   $46.30  
  7 purchase totals = $834.19       $881.6515   $881.65   $881.65   $881.70