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	$119.98	10.583%	$132.6775	$132.68	$132.70	$132.70
Purchase #2	$127.85	13.625%	$145.2696	$145.27	$145.25	$145.30
Purchase #3	$88.73	13.332%	$100.5595	$100.56	$100.55	$100.60
Purchase #4	$18.61	5.836%	$19.6961	$19.70	$19.70	$19.70
Purchase #5	$196.84	13.519%	$223.4508	$223.45	$223.45	$223.50
Purchase #6	$17.86	13.219%	$20.2209	$20.22	$20.20	$20.20
Purchase #7	$199.81	11.649%	$223.0859	$223.09	$223.10	$223.10
7 purchase totals =	$769.68		$864.9603	$864.97	$864.95	$865.10