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 $216.79   9.510%   $237.4067   $237.41   $237.40   $237.40  
  Purchase #2 $73.60   3.259%   $75.9986   $76.00   $76.00   $76.00  
  Purchase #3 $49.70   8.531%   $53.9399   $53.94   $53.95   $53.90  
  Purchase #4 $207.83   11.564%   $231.8635   $231.86   $231.85   $231.90  
  Purchase #5 $97.92   8.371%   $106.1169   $106.12   $106.10   $106.10  
  Purchase #6 $119.39   3.231%   $123.2475   $123.25   $123.25   $123.20  
  Purchase #7 $177.97   10.166%   $196.0624   $196.06   $196.05   $196.10  
  7 purchase totals = $943.20       $1,024.6355   $1,024.64   $1,024.60   $1,024.60