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 $62.25   4.728%   $65.1932   $65.19   $65.20   $65.20  
  Purchase #2 $186.54   5.163%   $196.1711   $196.17   $196.15   $196.20  
  Purchase #3 $209.81   8.453%   $227.5452   $227.55   $227.55   $227.50  
  Purchase #4 $6.73   4.827%   $7.0549   $7.05   $7.05   $7.10  
  Purchase #5 $62.93   4.548%   $65.7921   $65.79   $65.80   $65.80  
  Purchase #6 $86.39   6.461%   $91.9717   $91.97   $91.95   $92.00  
  Purchase #7 $136.68   8.426%   $148.1967   $148.20   $148.20   $148.20  
  7 purchase totals = $751.33       $801.9249   $801.92   $801.90   $802.00