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	$193.79	3.616%	$200.7974	$200.80	$200.80	$200.80
Purchase #2	$131.76	9.678%	$144.5117	$144.51	$144.50	$144.50
Purchase #3	$172.60	4.158%	$179.7767	$179.78	$179.80	$179.80
Purchase #4	$163.92	5.852%	$173.5126	$173.51	$173.50	$173.50
Purchase #5	$59.95	4.678%	$62.7545	$62.75	$62.75	$62.80
Purchase #6	$97.65	6.557%	$104.0529	$104.05	$104.05	$104.10
Purchase #7	$224.42	12.787%	$253.1166	$253.12	$253.10	$253.10
7 purchase totals =	$1,044.09		$1,118.5224	$1,118.52	$1,118.50	$1,118.60