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	$16.76	13.635%	$19.0452	$19.05	$19.05	$19.00
Purchase #2	$118.81	11.230%	$132.1524	$132.15	$132.15	$132.20
Purchase #3	$175.84	8.237%	$190.3239	$190.32	$190.30	$190.30
Purchase #4	$29.37	4.356%	$30.6494	$30.65	$30.65	$30.60
Purchase #5	$52.92	12.475%	$59.5218	$59.52	$59.50	$59.50
Purchase #6	$161.39	13.144%	$182.6031	$182.60	$182.60	$182.60
Purchase #7	$112.39	13.297%	$127.3345	$127.33	$127.35	$127.30
7 purchase totals =	$667.48		$741.6303	$741.62	$741.60	$741.50