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 $93.40   3.316%   $96.4971   $96.50   $96.50   $96.50  
  Purchase #2 $43.49   4.164%   $45.3009   $45.30   $45.30   $45.30  
  Purchase #3 $168.96   4.711%   $176.9197   $176.92   $176.90   $176.90  
  Purchase #4 $142.99   7.477%   $153.6814   $153.68   $153.70   $153.70  
  Purchase #5 $21.89   12.175%   $24.5551   $24.56   $24.55   $24.60  
  Purchase #6 $101.80   6.771%   $108.6929   $108.69   $108.70   $108.70  
  Purchase #7 $146.25   3.358%   $151.1611   $151.16   $151.15   $151.20  
  7 purchase totals = $718.78       $756.8082   $756.81   $756.80   $756.90