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 $72.69   5.290%   $76.5353   $76.54   $76.55   $76.50  
  Purchase #2 $168.67   11.567%   $188.1801   $188.18   $188.20   $188.20  
  Purchase #3 $63.44   7.165%   $67.9855   $67.99   $68.00   $68.00  
  Purchase #4 $205.90   10.592%   $227.7089   $227.71   $227.70   $227.70  
  Purchase #5 $142.47   8.352%   $154.3691   $154.37   $154.35   $154.40  
  Purchase #6 $10.87   8.110%   $11.7516   $11.75   $11.75   $11.80  
  Purchase #7 $43.78   11.511%   $48.8195   $48.82   $48.80   $48.80  
  7 purchase totals = $707.82       $775.3500   $775.36   $775.35   $775.40