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	$183.38	9.501%	$200.8029	$200.80	$200.80	$200.80
Purchase #2	$135.42	13.433%	$153.611	$153.61	$153.60	$153.60
Purchase #3	$207.46	11.495%	$231.3075	$231.31	$231.30	$231.30
Purchase #4	$158.47	3.839%	$164.5537	$164.55	$164.55	$164.60
Purchase #5	$96.55	9.807%	$106.0187	$106.02	$106.00	$106.00
Purchase #6	$100.43	11.327%	$111.8057	$111.81	$111.80	$111.80
Purchase #7	$174.56	7.346%	$187.3832	$187.38	$187.40	$187.40
7 purchase totals =	$1,056.27		$1,155.4827	$1,155.48	$1,155.45	$1,155.50