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	$237.35	7.340%	$254.7715	$254.77	$254.75	$254.80
Purchase #2	$173.65	9.615%	$190.3464	$190.35	$190.35	$190.30
Purchase #3	$234.71	10.838%	$260.1479	$260.15	$260.15	$260.10
Purchase #4	$45.86	5.565%	$48.4121	$48.41	$48.40	$48.40
Purchase #5	$209.25	13.827%	$238.183	$238.18	$238.20	$238.20
Purchase #6	$86.80	3.168%	$89.5498	$89.55	$89.55	$89.50
Purchase #7	$78.95	11.523%	$88.0474	$88.05	$88.05	$88.00
7 purchase totals =	$1,066.57		$1,169.4581	$1,169.46	$1,169.45	$1,169.30