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	$101.67	9.584%	$111.4141	$111.41	$111.40	$111.40
Purchase #2	$32.70	10.629%	$36.1757	$36.18	$36.20	$36.20
Purchase #3	$177.38	8.333%	$192.1611	$192.16	$192.15	$192.20
Purchase #4	$224.77	13.236%	$254.5206	$254.52	$254.50	$254.50
Purchase #5	$19.34	7.619%	$20.8135	$20.81	$20.80	$20.80
Purchase #6	$236.77	10.670%	$262.0334	$262.03	$262.05	$262.00
Purchase #7	$159.94	8.384%	$173.3494	$173.35	$173.35	$173.30
7 purchase totals =	$952.57		$1,050.4678	$1,050.46	$1,050.45	$1,050.40