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	$137.52	5.365%	$144.8979	$144.90	$144.90	$144.90
Purchase #2	$144.61	11.260%	$160.8931	$160.89	$160.90	$160.90
Purchase #3	$46.27	3.731%	$47.9963	$48.00	$48.00	$48.00
Purchase #4	$185.80	5.761%	$196.5039	$196.50	$196.50	$196.50
Purchase #5	$167.80	8.246%	$181.6368	$181.64	$181.65	$181.60
Purchase #6	$233.37	12.447%	$262.4176	$262.42	$262.40	$262.40
Purchase #7	$156.34	10.839%	$173.2857	$173.29	$173.30	$173.30
7 purchase totals =	$1,071.71		$1,167.6313	$1,167.64	$1,167.65	$1,167.60