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	$104.43	6.843%	$111.5761	$111.58	$111.60	$111.60
Purchase #2	$5.82	10.596%	$6.4367	$6.44	$6.45	$6.40
Purchase #3	$148.27	8.267%	$160.5275	$160.53	$160.55	$160.50
Purchase #4	$120.30	8.416%	$130.4244	$130.42	$130.40	$130.40
Purchase #5	$189.97	3.176%	$196.0034	$196.00	$196.00	$196.00
Purchase #6	$22.42	9.729%	$24.6012	$24.60	$24.60	$24.60
Purchase #7	$200.29	8.320%	$216.9541	$216.95	$216.95	$217.00
7 purchase totals =	$791.50		$846.5234	$846.52	$846.55	$846.50