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	$10.79	13.417%	$12.2377	$12.24	$12.25	$12.20
Purchase #2	$11.75	13.477%	$13.3335	$13.33	$13.35	$13.30
Purchase #3	$59.57	13.297%	$67.491	$67.49	$67.50	$67.50
Purchase #4	$53.30	7.606%	$57.354	$57.35	$57.35	$57.40
Purchase #5	$100.49	11.361%	$111.9067	$111.91	$111.90	$111.90
Purchase #6	$26.77	3.558%	$27.7225	$27.72	$27.70	$27.70
Purchase #7	$178.99	5.714%	$189.2175	$189.22	$189.20	$189.20
7 purchase totals =	$441.66		$479.2629	$479.26	$479.25	$479.20