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	$90.64	12.615%	$102.0742	$102.07	$102.05	$102.10
Purchase #2	$130.90	6.506%	$139.4164	$139.42	$139.40	$139.40
Purchase #3	$22.52	13.698%	$25.6048	$25.60	$25.60	$25.60
Purchase #4	$30.99	13.256%	$35.098	$35.10	$35.10	$35.10
Purchase #5	$111.93	3.747%	$116.124	$116.12	$116.10	$116.10
Purchase #6	$221.92	3.159%	$228.9305	$228.93	$228.95	$228.90
Purchase #7	$112.62	5.718%	$119.0596	$119.06	$119.05	$119.10
7 purchase totals =	$721.52		$766.3075	$766.30	$766.25	$766.30