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	$216.89	11.702%	$242.2705	$242.27	$242.25	$242.30
Purchase #2	$192.54	11.429%	$214.5454	$214.55	$214.55	$214.50
Purchase #3	$39.57	6.291%	$42.0593	$42.06	$42.05	$42.10
Purchase #4	$61.76	3.821%	$64.1198	$64.12	$64.10	$64.10
Purchase #5	$130.88	13.347%	$148.3486	$148.35	$148.35	$148.30
Purchase #6	$48.62	10.701%	$53.8228	$53.82	$53.80	$53.80
Purchase #7	$18.27	5.523%	$19.2791	$19.28	$19.30	$19.30
7 purchase totals =	$708.53		$784.4455	$784.45	$784.40	$784.40