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	$158.62	9.851%	$174.2457	$174.25	$174.25	$174.20
Purchase #2	$104.43	7.113%	$111.8581	$111.86	$111.85	$111.90
Purchase #3	$207.72	6.592%	$221.4129	$221.41	$221.40	$221.40
Purchase #4	$174.52	5.462%	$184.0523	$184.05	$184.05	$184.10
Purchase #5	$161.65	3.503%	$167.3126	$167.31	$167.30	$167.30
Purchase #6	$111.45	7.493%	$119.8009	$119.80	$119.80	$119.80
Purchase #7	$104.92	3.433%	$108.5219	$108.52	$108.50	$108.50
7 purchase totals =	$1,023.31		$1,087.2044	$1,087.20	$1,087.15	$1,087.20