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	$184.72	5.826%	$195.4818	$195.48	$195.50	$195.50
Purchase #2	$156.64	11.186%	$174.1618	$174.16	$174.15	$174.20
Purchase #3	$156.49	10.182%	$172.4238	$172.42	$172.40	$172.40
Purchase #4	$76.43	9.810%	$83.9278	$83.93	$83.95	$83.90
Purchase #5	$230.26	10.243%	$253.8455	$253.85	$253.85	$253.80
Purchase #6	$74.57	10.686%	$82.5386	$82.54	$82.55	$82.50
Purchase #7	$41.49	5.414%	$43.7363	$43.74	$43.75	$43.70
7 purchase totals =	$920.60		$1,006.1156	$1,006.12	$1,006.15	$1,006.00