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	$199.33	10.119%	$219.5002	$219.50	$219.50	$219.50
Purchase #2	$193.94	4.246%	$202.1747	$202.17	$202.15	$202.20
Purchase #3	$69.30	4.771%	$72.6063	$72.61	$72.60	$72.60
Purchase #4	$48.77	11.694%	$54.4732	$54.47	$54.45	$54.50
Purchase #5	$231.32	8.378%	$250.7	$250.70	$250.70	$250.70
Purchase #6	$184.92	9.316%	$202.1471	$202.15	$202.15	$202.10
Purchase #7	$62.45	12.579%	$70.3056	$70.31	$70.30	$70.30
7 purchase totals =	$990.03		$1,071.9071	$1,071.91	$1,071.85	$1,071.90