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	$9.56	12.227%	$10.7289	$10.73	$10.75	$10.70
Purchase #2	$5.35	4.118%	$5.5703	$5.57	$5.55	$5.60
Purchase #3	$30.67	4.795%	$32.1406	$32.14	$32.15	$32.10
Purchase #4	$165.85	9.104%	$180.949	$180.95	$180.95	$180.90
Purchase #5	$56.95	13.303%	$64.5261	$64.53	$64.55	$64.50
Purchase #6	$241.34	10.852%	$267.5302	$267.53	$267.55	$267.50
Purchase #7	$105.77	5.520%	$111.6085	$111.61	$111.60	$111.60
7 purchase totals =	$615.49		$673.0536	$673.06	$673.10	$672.90