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 $93.95   11.453%   $104.7101   $104.71   $104.70   $104.70  
  Purchase #2 $29.30   3.146%   $30.2218   $30.22   $30.20   $30.20  
  Purchase #3 $9.90   5.219%   $10.4167   $10.42   $10.40   $10.40  
  Purchase #4 $87.99   9.687%   $96.5136   $96.51   $96.50   $96.50  
  Purchase #5 $227.33   6.743%   $242.6589   $242.66   $242.65   $242.70  
  Purchase #6 $212.84   5.387%   $224.3057   $224.31   $224.30   $224.30  
  Purchase #7 $44.48   8.406%   $48.219   $48.22   $48.20   $48.20  
  7 purchase totals = $705.79       $757.0458   $757.05   $756.95   $757.00