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	$48.98	9.175%	$53.4739	$53.47	$53.45	$53.50
Purchase #2	$159.39	10.254%	$175.7339	$175.73	$175.75	$175.70
Purchase #3	$126.51	4.286%	$131.9322	$131.93	$131.95	$131.90
Purchase #4	$49.55	5.692%	$52.3704	$52.37	$52.35	$52.40
Purchase #5	$105.45	8.860%	$114.7929	$114.79	$114.80	$114.80
Purchase #6	$60.78	6.745%	$64.8796	$64.88	$64.90	$64.90
Purchase #7	$132.52	7.632%	$142.6339	$142.63	$142.65	$142.60
7 purchase totals =	$683.18		$735.8168	$735.80	$735.85	$735.80