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	$145.64	3.324%	$150.4811	$150.48	$150.50	$150.50
Purchase #2	$84.37	12.162%	$94.6311	$94.63	$94.65	$94.60
Purchase #3	$66.51	8.444%	$72.1261	$72.13	$72.15	$72.10
Purchase #4	$106.57	4.576%	$111.4466	$111.45	$111.45	$111.40
Purchase #5	$137.92	6.866%	$147.3896	$147.39	$147.40	$147.40
Purchase #6	$190.75	3.118%	$196.6976	$196.70	$196.70	$196.70
Purchase #7	$100.49	3.130%	$103.6353	$103.64	$103.65	$103.60
7 purchase totals =	$832.25		$876.4074	$876.42	$876.50	$876.30