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	$149.85	10.403%	$165.4389	$165.44	$165.45	$165.40
Purchase #2	$167.81	11.518%	$187.1384	$187.14	$187.15	$187.10
Purchase #3	$11.76	9.612%	$12.8904	$12.89	$12.90	$12.90
Purchase #4	$29.40	10.789%	$32.572	$32.57	$32.55	$32.60
Purchase #5	$245.94	12.123%	$275.7553	$275.76	$275.75	$275.80
Purchase #6	$205.60	12.383%	$231.0594	$231.06	$231.05	$231.10
Purchase #7	$230.52	3.619%	$238.8625	$238.86	$238.85	$238.90
7 purchase totals =	$1,040.88		$1,143.7169	$1,143.72	$1,143.70	$1,143.80