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	$183.75	3.634%	$190.4275	$190.43	$190.45	$190.40
Purchase #2	$163.51	13.309%	$185.2715	$185.27	$185.25	$185.30
Purchase #3	$7.99	11.611%	$8.9177	$8.92	$8.90	$8.90
Purchase #4	$192.27	13.620%	$218.4572	$218.46	$218.45	$218.50
Purchase #5	$39.69	8.419%	$43.0315	$43.03	$43.05	$43.00
Purchase #6	$151.30	4.465%	$158.0555	$158.06	$158.05	$158.10
Purchase #7	$132.77	10.787%	$147.0919	$147.09	$147.10	$147.10
7 purchase totals =	$871.28		$951.2528	$951.26	$951.25	$951.30