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	$212.27	4.194%	$221.1726	$221.17	$221.15	$221.20
Purchase #2	$43.46	3.845%	$45.131	$45.13	$45.15	$45.10
Purchase #3	$190.46	9.527%	$208.6051	$208.61	$208.60	$208.60
Purchase #4	$202.34	4.851%	$212.1555	$212.16	$212.15	$212.20
Purchase #5	$125.42	6.238%	$133.2437	$133.24	$133.25	$133.20
Purchase #6	$62.49	12.754%	$70.46	$70.46	$70.45	$70.50
Purchase #7	$165.51	11.502%	$184.547	$184.55	$184.55	$184.50
7 purchase totals =	$1,001.95		$1,075.3149	$1,075.32	$1,075.30	$1,075.30