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	$193.89	9.653%	$212.6062	$212.61	$212.60	$212.60
Purchase #2	$89.27	12.639%	$100.5528	$100.55	$100.55	$100.60
Purchase #3	$17.72	8.595%	$19.243	$19.24	$19.25	$19.20
Purchase #4	$141.68	9.358%	$154.9384	$154.94	$154.95	$154.90
Purchase #5	$104.92	12.221%	$117.7423	$117.74	$117.75	$117.70
Purchase #6	$18.47	13.134%	$20.8958	$20.90	$20.90	$20.90
Purchase #7	$63.90	10.456%	$70.5814	$70.58	$70.60	$70.60
7 purchase totals =	$629.85		$696.5599	$696.56	$696.60	$696.50