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 $118.82   5.763%   $125.6676   $125.67   $125.65   $125.70  
  Purchase #2 $10.76   10.764%   $11.9182   $11.92   $11.90   $11.90  
  Purchase #3 $107.87   5.500%   $113.8029   $113.80   $113.80   $113.80  
  Purchase #4 $124.71   7.353%   $133.8799   $133.88   $133.90   $133.90  
  Purchase #5 $83.99   12.153%   $94.1973   $94.20   $94.20   $94.20  
  Purchase #6 $61.43   12.465%   $69.0872   $69.09   $69.10   $69.10  
  Purchase #7 $188.72   12.392%   $212.1062   $212.11   $212.10   $212.10  
  7 purchase totals = $696.30       $760.6593   $760.67   $760.65   $760.70