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	$196.78	8.417%	$213.343	$213.34	$213.35	$213.30
Purchase #2	$132.96	4.134%	$138.4566	$138.46	$138.45	$138.50
Purchase #3	$99.38	12.337%	$111.6405	$111.64	$111.65	$111.60
Purchase #4	$80.89	13.728%	$91.9946	$91.99	$92.00	$92.00
Purchase #5	$71.76	9.755%	$78.7602	$78.76	$78.75	$78.80
Purchase #6	$77.93	13.255%	$88.2596	$88.26	$88.25	$88.30
Purchase #7	$178.37	10.476%	$197.056	$197.06	$197.05	$197.10
7 purchase totals =	$838.07		$919.5105	$919.51	$919.50	$919.60