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	$141.50	9.872%	$155.4689	$155.47	$155.45	$155.50
Purchase #2	$10.91	4.633%	$11.4155	$11.42	$11.40	$11.40
Purchase #3	$48.96	10.780%	$54.2379	$54.24	$54.25	$54.20
Purchase #4	$101.82	3.612%	$105.4977	$105.50	$105.50	$105.50
Purchase #5	$115.34	10.527%	$127.4818	$127.48	$127.50	$127.50
Purchase #6	$100.43	12.229%	$112.7116	$112.71	$112.70	$112.70
Purchase #7	$46.71	7.861%	$50.3819	$50.38	$50.40	$50.40
7 purchase totals =	$565.67		$617.1953	$617.20	$617.20	$617.20