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	$56.47	9.735%	$61.9674	$61.97	$61.95	$62.00
Purchase #2	$102.85	11.316%	$114.4885	$114.49	$114.50	$114.50
Purchase #3	$54.94	10.251%	$60.5719	$60.57	$60.55	$60.60
Purchase #4	$71.86	9.584%	$78.7471	$78.75	$78.75	$78.70
Purchase #5	$106.25	9.853%	$116.7188	$116.72	$116.70	$116.70
Purchase #6	$37.52	6.467%	$39.9464	$39.95	$39.95	$39.90
Purchase #7	$13.96	11.428%	$15.5553	$15.56	$15.55	$15.60
7 purchase totals =	$443.85		$487.9954	$488.01	$487.95	$488.00