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	$209.97	8.834%	$228.5187	$228.52	$228.50	$228.50
Purchase #2	$9.72	5.874%	$10.291	$10.29	$10.30	$10.30
Purchase #3	$100.65	10.726%	$111.4457	$111.45	$111.45	$111.40
Purchase #4	$160.75	8.686%	$174.7127	$174.71	$174.70	$174.70
Purchase #5	$163.34	13.284%	$185.0381	$185.04	$185.05	$185.00
Purchase #6	$134.93	7.402%	$144.9175	$144.92	$144.90	$144.90
Purchase #7	$155.66	11.466%	$173.508	$173.51	$173.50	$173.50
7 purchase totals =	$935.02		$1,028.4317	$1,028.44	$1,028.40	$1,028.30