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	$59.64	4.820%	$62.5146	$62.51	$62.50	$62.50
Purchase #2	$237.26	9.785%	$260.4759	$260.48	$260.50	$260.50
Purchase #3	$202.78	13.846%	$230.8569	$230.86	$230.85	$230.90
Purchase #4	$164.54	8.706%	$178.8649	$178.86	$178.85	$178.90
Purchase #5	$110.36	5.589%	$116.528	$116.53	$116.55	$116.50
Purchase #6	$80.32	12.481%	$90.3447	$90.34	$90.35	$90.30
Purchase #7	$59.87	8.318%	$64.85	$64.85	$64.85	$64.90
7 purchase totals =	$914.77		$1,004.4350	$1,004.43	$1,004.45	$1,004.50