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	$151.82	10.278%	$167.4241	$167.42	$167.40	$167.40
Purchase #2	$191.69	13.572%	$217.7062	$217.71	$217.70	$217.70
Purchase #3	$235.88	5.412%	$248.6458	$248.65	$248.65	$248.60
Purchase #4	$99.82	11.423%	$111.2224	$111.22	$111.20	$111.20
Purchase #5	$141.93	11.492%	$158.2406	$158.24	$158.25	$158.20
Purchase #6	$146.29	6.274%	$155.4682	$155.47	$155.45	$155.50
Purchase #7	$151.57	13.146%	$171.4954	$171.50	$171.50	$171.50
7 purchase totals =	$1,119.00		$1,230.2027	$1,230.21	$1,230.15	$1,230.10