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	$77.86	9.619%	$85.3494	$85.35	$85.35	$85.30
Purchase #2	$109.95	8.717%	$119.5343	$119.53	$119.55	$119.50
Purchase #3	$12.50	3.255%	$12.9069	$12.91	$12.90	$12.90
Purchase #4	$103.49	7.380%	$111.1276	$111.13	$111.15	$111.10
Purchase #5	$150.35	5.871%	$159.177	$159.18	$159.20	$159.20
Purchase #6	$236.56	6.774%	$252.5846	$252.58	$252.60	$252.60
Purchase #7	$94.91	8.699%	$103.1662	$103.17	$103.15	$103.20
7 purchase totals =	$785.62		$843.8460	$843.85	$843.90	$843.80