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	$230.94	9.194%	$252.1726	$252.17	$252.15	$252.20
Purchase #2	$237.73	7.617%	$255.8379	$255.84	$255.85	$255.80
Purchase #3	$80.30	4.335%	$83.781	$83.78	$83.80	$83.80
Purchase #4	$136.77	13.511%	$155.249	$155.25	$155.25	$155.20
Purchase #5	$89.53	6.121%	$95.0101	$95.01	$95.00	$95.00
Purchase #6	$141.45	7.395%	$151.9102	$151.91	$151.90	$151.90
Purchase #7	$230.63	13.131%	$260.914	$260.91	$260.90	$260.90
7 purchase totals =	$1,147.35		$1,254.8748	$1,254.87	$1,254.85	$1,254.80