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	$160.92	7.309%	$172.6816	$172.68	$172.70	$172.70
Purchase #2	$68.39	7.363%	$73.4256	$73.43	$73.45	$73.40
Purchase #3	$36.38	13.168%	$41.1705	$41.17	$41.15	$41.20
Purchase #4	$36.68	10.603%	$40.5692	$40.57	$40.55	$40.60
Purchase #5	$136.52	4.391%	$142.5146	$142.51	$142.50	$142.50
Purchase #6	$226.26	10.507%	$250.0331	$250.03	$250.05	$250.00
Purchase #7	$132.25	7.564%	$142.2534	$142.25	$142.25	$142.30
7 purchase totals =	$797.40		$862.6480	$862.64	$862.65	$862.70