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	$99.89	11.633%	$111.5102	$111.51	$111.50	$111.50
Purchase #2	$14.62	3.638%	$15.1519	$15.15	$15.15	$15.20
Purchase #3	$17.90	12.425%	$20.1241	$20.12	$20.10	$20.10
Purchase #4	$64.49	6.779%	$68.8618	$68.86	$68.85	$68.90
Purchase #5	$115.28	10.125%	$126.9521	$126.95	$126.95	$127.00
Purchase #6	$18.82	9.437%	$20.596	$20.60	$20.60	$20.60
Purchase #7	$98.78	3.717%	$102.4517	$102.45	$102.45	$102.50
7 purchase totals =	$429.78		$465.6478	$465.64	$465.60	$465.80