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 $185.84   5.451%   $195.9701   $195.97   $195.95   $196.00  
  Purchase #2 $97.37   4.175%   $101.4352   $101.44   $101.45   $101.40  
  Purchase #3 $127.85   6.503%   $136.1641   $136.16   $136.15   $136.20  
  Purchase #4 $97.99   7.174%   $105.0198   $105.02   $105.00   $105.00  
  Purchase #5 $56.36   3.195%   $58.1607   $58.16   $58.15   $58.20  
  Purchase #6 $60.47   5.794%   $63.9736   $63.97   $63.95   $64.00  
  Purchase #7 $101.61   4.791%   $106.4781   $106.48   $106.50   $106.50  
  7 purchase totals = $727.49       $767.2016   $767.20   $767.15   $767.30