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	$241.50	13.494%	$274.088	$274.09	$274.10	$274.10
Purchase #2	$100.43	4.434%	$104.8831	$104.88	$104.90	$104.90
Purchase #3	$119.78	6.486%	$127.5489	$127.55	$127.55	$127.50
Purchase #4	$26.27	9.291%	$28.7107	$28.71	$28.70	$28.70
Purchase #5	$221.51	3.758%	$229.8343	$229.83	$229.85	$229.80
Purchase #6	$222.82	6.833%	$238.0453	$238.05	$238.05	$238.00
Purchase #7	$52.67	8.358%	$57.0722	$57.07	$57.05	$57.10
7 purchase totals =	$984.98		$1,060.1825	$1,060.18	$1,060.20	$1,060.10