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	$105.31	10.559%	$116.4297	$116.43	$116.45	$116.40
Purchase #2	$79.44	4.695%	$83.1697	$83.17	$83.15	$83.20
Purchase #3	$53.46	8.565%	$58.0388	$58.04	$58.05	$58.00
Purchase #4	$161.71	6.522%	$172.2567	$172.26	$172.25	$172.30
Purchase #5	$146.46	12.479%	$164.7367	$164.74	$164.75	$164.70
Purchase #6	$127.88	3.510%	$132.3686	$132.37	$132.35	$132.40
Purchase #7	$223.43	6.865%	$238.7685	$238.77	$238.75	$238.80
7 purchase totals =	$897.69		$965.7687	$965.78	$965.75	$965.80