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	$39.58	10.142%	$43.5942	$43.59	$43.60	$43.60
Purchase #2	$69.27	3.182%	$71.4742	$71.47	$71.45	$71.50
Purchase #3	$32.70	7.227%	$35.0632	$35.06	$35.05	$35.10
Purchase #4	$47.67	9.661%	$52.2754	$52.28	$52.30	$52.30
Purchase #5	$183.79	8.848%	$200.0517	$200.05	$200.05	$200.10
Purchase #6	$244.32	8.517%	$265.1287	$265.13	$265.15	$265.10
Purchase #7	$13.55	12.821%	$15.2872	$15.29	$15.30	$15.30
7 purchase totals =	$630.88		$682.8746	$682.87	$682.90	$683.00