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	$158.95	5.717%	$168.0372	$168.04	$168.05	$168.00
Purchase #2	$87.77	12.385%	$98.6403	$98.64	$98.65	$98.60
Purchase #3	$119.81	6.136%	$127.1615	$127.16	$127.15	$127.20
Purchase #4	$52.89	3.435%	$54.7068	$54.71	$54.70	$54.70
Purchase #5	$207.60	4.196%	$216.3109	$216.31	$216.30	$216.30
Purchase #6	$10.72	12.227%	$12.0307	$12.03	$12.05	$12.00
Purchase #7	$173.39	11.566%	$193.4443	$193.44	$193.45	$193.40
7 purchase totals =	$811.13		$870.3317	$870.33	$870.35	$870.20