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	$181.80	3.803%	$188.7139	$188.71	$188.70	$188.70
Purchase #2	$174.72	6.329%	$185.778	$185.78	$185.80	$185.80
Purchase #3	$106.87	11.176%	$118.8138	$118.81	$118.80	$118.80
Purchase #4	$205.34	7.379%	$220.492	$220.49	$220.50	$220.50
Purchase #5	$131.60	8.628%	$142.9544	$142.95	$142.95	$143.00
Purchase #6	$135.94	11.149%	$151.096	$151.10	$151.10	$151.10
Purchase #7	$150.85	10.301%	$166.3891	$166.39	$166.40	$166.40
7 purchase totals =	$1,087.12		$1,174.2372	$1,174.23	$1,174.25	$1,174.30