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	$207.85	13.244%	$235.3777	$235.38	$235.40	$235.40
Purchase #2	$30.47	11.317%	$33.9183	$33.92	$33.90	$33.90
Purchase #3	$136.49	4.745%	$142.9665	$142.97	$142.95	$143.00
Purchase #4	$28.77	5.530%	$30.361	$30.36	$30.35	$30.40
Purchase #5	$215.48	3.103%	$222.1663	$222.17	$222.15	$222.20
Purchase #6	$106.46	4.630%	$111.3891	$111.39	$111.40	$111.40
Purchase #7	$155.58	13.461%	$176.5226	$176.52	$176.50	$176.50
7 purchase totals =	$881.10		$952.7015	$952.71	$952.65	$952.80