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	$226.94	10.433%	$250.6167	$250.62	$250.60	$250.60
Purchase #2	$234.73	4.763%	$245.9102	$245.91	$245.90	$245.90
Purchase #3	$78.25	5.134%	$82.2674	$82.27	$82.25	$82.30
Purchase #4	$11.51	3.635%	$11.9284	$11.93	$11.95	$11.90
Purchase #5	$175.55	8.331%	$190.1751	$190.18	$190.20	$190.20
Purchase #6	$111.80	13.639%	$127.0484	$127.05	$127.05	$127.00
Purchase #7	$133.72	7.847%	$144.213	$144.21	$144.20	$144.20
7 purchase totals =	$972.50		$1,052.1592	$1,052.17	$1,052.15	$1,052.10