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	$101.25	3.762%	$105.059	$105.06	$105.05	$105.10
Purchase #2	$191.88	12.552%	$215.9648	$215.96	$215.95	$216.00
Purchase #3	$200.30	8.564%	$217.4537	$217.45	$217.45	$217.50
Purchase #4	$217.68	10.390%	$240.297	$240.30	$240.30	$240.30
Purchase #5	$77.73	9.448%	$85.0739	$85.07	$85.05	$85.10
Purchase #6	$12.68	10.142%	$13.966	$13.97	$13.95	$14.00
Purchase #7	$107.78	8.131%	$116.5436	$116.54	$116.55	$116.50
7 purchase totals =	$909.30		$994.3580	$994.35	$994.30	$994.50