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	$220.74	3.538%	$228.5498	$228.55	$228.55	$228.50
Purchase #2	$23.59	9.284%	$25.7801	$25.78	$25.80	$25.80
Purchase #3	$164.47	8.763%	$178.8825	$178.88	$178.90	$178.90
Purchase #4	$170.74	7.208%	$183.0469	$183.05	$183.05	$183.00
Purchase #5	$88.88	13.510%	$100.8877	$100.89	$100.90	$100.90
Purchase #6	$229.53	3.452%	$237.4534	$237.45	$237.45	$237.50
Purchase #7	$226.83	12.698%	$255.6329	$255.63	$255.65	$255.60
7 purchase totals =	$1,124.78		$1,210.2333	$1,210.23	$1,210.30	$1,210.20