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	$216.91	5.599%	$229.0548	$229.05	$229.05	$229.10
Purchase #2	$172.26	13.417%	$195.3721	$195.37	$195.35	$195.40
Purchase #3	$63.28	6.287%	$67.2584	$67.26	$67.25	$67.30
Purchase #4	$105.84	5.398%	$111.5532	$111.55	$111.55	$111.60
Purchase #5	$113.73	11.724%	$127.0637	$127.06	$127.05	$127.10
Purchase #6	$188.69	10.554%	$208.6043	$208.60	$208.60	$208.60
Purchase #7	$232.39	12.176%	$260.6858	$260.69	$260.70	$260.70
7 purchase totals =	$1,093.10		$1,199.5923	$1,199.58	$1,199.55	$1,199.80