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	$75.76	13.275%	$85.8171	$85.82	$85.80	$85.80
Purchase #2	$35.29	3.554%	$36.5442	$36.54	$36.55	$36.50
Purchase #3	$99.58	11.851%	$111.3812	$111.38	$111.40	$111.40
Purchase #4	$145.95	5.728%	$154.31	$154.31	$154.30	$154.30
Purchase #5	$178.81	7.717%	$192.6088	$192.61	$192.60	$192.60
Purchase #6	$18.40	4.168%	$19.1669	$19.17	$19.15	$19.20
Purchase #7	$123.75	10.868%	$137.1992	$137.20	$137.20	$137.20
7 purchase totals =	$677.54		$737.0274	$737.03	$737.00	$737.00