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	$48.78	12.558%	$54.9058	$54.91	$54.90	$54.90
Purchase #2	$235.45	3.807%	$244.4136	$244.41	$244.40	$244.40
Purchase #3	$88.65	11.196%	$98.5753	$98.58	$98.60	$98.60
Purchase #4	$130.69	7.266%	$140.1859	$140.19	$140.20	$140.20
Purchase #5	$169.55	13.275%	$192.0578	$192.06	$192.05	$192.10
Purchase #6	$212.90	8.223%	$230.4068	$230.41	$230.40	$230.40
Purchase #7	$114.83	8.732%	$124.857	$124.86	$124.85	$124.90
7 purchase totals =	$1,000.85		$1,085.4022	$1,085.42	$1,085.40	$1,085.50