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	$142.60	11.267%	$158.6667	$158.67	$158.65	$158.70
Purchase #2	$131.71	7.610%	$141.7331	$141.73	$141.75	$141.70
Purchase #3	$10.57	4.437%	$11.039	$11.04	$11.05	$11.00
Purchase #4	$73.30	13.191%	$82.969	$82.97	$82.95	$83.00
Purchase #5	$39.76	10.537%	$43.9495	$43.95	$43.95	$43.90
Purchase #6	$142.70	8.716%	$155.1377	$155.14	$155.15	$155.10
Purchase #7	$50.56	7.815%	$54.5113	$54.51	$54.50	$54.50
7 purchase totals =	$591.20		$648.0063	$648.01	$648.00	$647.90