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 $161.87   8.235%   $175.2   $175.20   $175.20   $175.20  
  Purchase #2 $90.90   8.650%   $98.7629   $98.76   $98.75   $98.80  
  Purchase #3 $132.83   4.740%   $139.1261   $139.13   $139.15   $139.10  
  Purchase #4 $93.43   8.398%   $101.2763   $101.28   $101.30   $101.30  
  Purchase #5 $10.88   6.183%   $11.5527   $11.55   $11.55   $11.60  
  Purchase #6 $60.66   5.419%   $63.9472   $63.95   $63.95   $63.90  
  Purchase #7 $166.73   6.251%   $177.1523   $177.15   $177.15   $177.20  
  7 purchase totals = $717.30       $767.0175   $767.02   $767.05   $767.10