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	$157.39	5.258%	$165.6656	$165.67	$165.65	$165.70
Purchase #2	$161.96	6.727%	$172.855	$172.86	$172.85	$172.90
Purchase #3	$160.87	7.543%	$173.0044	$173.00	$173.00	$173.00
Purchase #4	$171.98	3.125%	$177.3544	$177.35	$177.35	$177.40
Purchase #5	$90.70	12.369%	$101.9187	$101.92	$101.90	$101.90
Purchase #6	$133.65	7.697%	$143.937	$143.94	$143.95	$143.90
Purchase #7	$142.60	6.407%	$151.7364	$151.74	$151.75	$151.70
7 purchase totals =	$1,019.15		$1,086.4715	$1,086.48	$1,086.45	$1,086.50