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	$48.36	8.461%	$52.4517	$52.45	$52.45	$52.50
Purchase #2	$132.31	9.293%	$144.6056	$144.61	$144.60	$144.60
Purchase #3	$92.61	13.540%	$105.1494	$105.15	$105.15	$105.10
Purchase #4	$149.49	6.688%	$159.4879	$159.49	$159.50	$159.50
Purchase #5	$47.63	10.541%	$52.6507	$52.65	$52.65	$52.70
Purchase #6	$176.87	12.615%	$199.1822	$199.18	$199.20	$199.20
Purchase #7	$75.69	6.828%	$80.8581	$80.86	$80.85	$80.90
7 purchase totals =	$722.96		$794.3856	$794.39	$794.40	$794.50