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	$157.90	12.191%	$177.1496	$177.15	$177.15	$177.10
Purchase #2	$231.36	11.593%	$258.1816	$258.18	$258.20	$258.20
Purchase #3	$73.37	7.178%	$78.6365	$78.64	$78.65	$78.60
Purchase #4	$47.60	12.724%	$53.6566	$53.66	$53.65	$53.70
Purchase #5	$99.85	5.585%	$105.4266	$105.43	$105.45	$105.40
Purchase #6	$110.92	12.162%	$124.4101	$124.41	$124.40	$124.40
Purchase #7	$232.78	9.346%	$254.5356	$254.54	$254.55	$254.50
7 purchase totals =	$953.78		$1,051.9966	$1,052.01	$1,052.05	$1,051.90