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	$32.61	9.728%	$35.7823	$35.78	$35.80	$35.80
Purchase #2	$11.80	4.624%	$12.3456	$12.35	$12.35	$12.30
Purchase #3	$220.29	9.611%	$241.4621	$241.46	$241.45	$241.50
Purchase #4	$102.65	13.406%	$116.4113	$116.41	$116.40	$116.40
Purchase #5	$220.92	3.286%	$228.1794	$228.18	$228.20	$228.20
Purchase #6	$56.85	4.284%	$59.2855	$59.29	$59.30	$59.30
Purchase #7	$10.94	7.743%	$11.7871	$11.79	$11.80	$11.80
7 purchase totals =	$656.06		$705.2533	$705.26	$705.30	$705.30