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	$219.76	4.839%	$230.3942	$230.39	$230.40	$230.40
Purchase #2	$126.68	13.131%	$143.3144	$143.31	$143.30	$143.30
Purchase #3	$147.96	12.685%	$166.7287	$166.73	$166.75	$166.70
Purchase #4	$74.93	13.528%	$85.0665	$85.07	$85.05	$85.10
Purchase #5	$202.31	9.316%	$221.1572	$221.16	$221.15	$221.20
Purchase #6	$62.80	13.321%	$71.1656	$71.17	$71.15	$71.20
Purchase #7	$129.25	11.252%	$143.7932	$143.79	$143.80	$143.80
7 purchase totals =	$963.69		$1,061.6198	$1,061.62	$1,061.60	$1,061.70