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	$192.83	13.586%	$219.0279	$219.03	$219.05	$219.00
Purchase #2	$73.79	6.559%	$78.6299	$78.63	$78.65	$78.60
Purchase #3	$20.72	4.350%	$21.6213	$21.62	$21.60	$21.60
Purchase #4	$238.61	6.724%	$254.6541	$254.65	$254.65	$254.70
Purchase #5	$27.32	4.129%	$28.448	$28.45	$28.45	$28.40
Purchase #6	$131.45	8.686%	$142.8677	$142.87	$142.85	$142.90
Purchase #7	$231.76	9.305%	$253.3253	$253.33	$253.35	$253.30
7 purchase totals =	$916.48		$998.5742	$998.58	$998.60	$998.50